Enable split heap in K64F/K66F devices

-Enable MBED_SPLIT_HEAP for K64F and K66F
-Allow GCC_ARM toolchain to utilize remaining 64K memory area
-Make ARM toolchain to start memory filling from 64K region to leave
 more space to bigger 192K region.

targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_K66F/device/TOOLCHAIN_ARM_STD/MK66FN2M0xxx18.sct

@@ -114,12 +114,12 @@ LR_IROM1 m_interrupts_start m_text_start+m_text_size-m_interrupts_start {   ; lo
   RW_m_crash_data m_crash_report_ram_start EMPTY m_crash_report_ram_size { ; RW data
   }
   RW_m_data m_data_start m_data_size { ; RW data
-    .ANY (+RW +ZI)
+    .ANY2 (+RW +ZI)
   }
   RW_m_data_2 m_data_2_start m_data_2_size { ; RW data
-    .ANY (+RW +ZI)
+    .ANY1 (+RW +ZI)
   }
-  RW_IRAM1 ImageLimit(RW_m_data_2) {
+  RW_IRAM1 ImageLimit(RW_m_data_2) EMPTY 0 {
   }
   ARM_LIB_HEAP AlignExpr(+0, 16) EMPTY (m_data_2_start + m_data_2_size - Stack_Size - AlignExpr(ImageLimit(RW_IRAM1), 16)) { ; Heap region growing up
   }

targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_K66F/device/TOOLCHAIN_GCC_ARM/MK66FN2M0xxx18.ld

@@ -210,6 +210,14 @@ SECTIONS
     __CRASH_DATA_RAM_END__ = .; /* Define a global symbol at data end */
   } > m_data
 
+  .heap_0 :
+  {
+    . = ALIGN(8);
+    __mbed_sbrk_start_0 = .;
+    . += (ORIGIN(m_data) + LENGTH(m_data) - .);
+    __mbed_krbs_start_0 = .;
+  } > m_data
+
   __VECTOR_RAM = DEFINED(__ram_vector_table__) ? __VECTOR_RAM__ : ORIGIN(m_interrupts);
   __RAM_VECTOR_TABLE_SIZE_BYTES = DEFINED(__ram_vector_table__) ? (__interrupts_ram_end__ - __interrupts_ram_start__) : 0x0;
 
@@ -249,8 +257,10 @@ SECTIONS
     . = ALIGN(8);
     __end__ = .;
     PROVIDE(end = .);
+    __mbed_sbrk_start = .;
     __HeapBase = .;
     . = ORIGIN(m_data_2) + LENGTH(m_data_2) - STACK_SIZE;
+    __mbed_krbs_start = .;
     __HeapLimit = .;
     __heap_limit = .; /* Add for _sbrk */
   } > m_data_2

targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_MCU_K64F/device/TOOLCHAIN_ARM_STD/MK64FN1M0xxx12.sct

@@ -118,12 +118,12 @@ LR_IROM1 m_interrupts_start m_text_start+m_text_size-m_interrupts_start { ; load
   RW_m_crash_data m_crash_report_ram_start EMPTY m_crash_report_ram_size { ; RW data
   } 
   RW_m_data m_data_start m_data_size { ; RW data
-    .ANY (+RW +ZI)
+    .ANY2 (+RW +ZI)
   }
   RW_m_data_2 m_data_2_start m_data_2_size { ; RW data
-    .ANY (+RW +ZI)
+    .ANY1 (+RW +ZI)
   }
-  RW_IRAM1 ImageLimit(RW_m_data_2) {
+  RW_IRAM1 ImageLimit(RW_m_data_2) EMPTY 0 {
   }
   ARM_LIB_HEAP AlignExpr(+0, 16) EMPTY (m_data_2_start + m_data_2_size - Stack_Size - AlignExpr(ImageLimit(RW_IRAM1), 16)) { ; Heap region growing up
   }

targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_MCU_K64F/device/TOOLCHAIN_GCC_ARM/MK64FN1M0xxx12.ld

@@ -196,7 +196,7 @@ SECTIONS
     . = ALIGN(8);
     __interrupts_ram_end__ = .; /* Define a global symbol at data end */
   } > m_data
-  
+
   .crash_data_ram :
   {
     . = ALIGN(8);
@@ -209,6 +209,13 @@ SECTIONS
     __CRASH_DATA_RAM_END__ = .; /* Define a global symbol at data end */
   } > m_data
 
+  .heap_0 :
+  {
+    . = ALIGN(8);
+    __mbed_sbrk_start_0 = .;
+    . += (ORIGIN(m_data) + LENGTH(m_data) - .);
+    __mbed_krbs_start_0 = .;
+  } > m_data
 
   __VECTOR_RAM = DEFINED(__ram_vector_table__) ? __VECTOR_RAM__ : ORIGIN(m_interrupts);
   __RAM_VECTOR_TABLE_SIZE_BYTES = DEFINED(__ram_vector_table__) ? (__interrupts_ram_end__ - __interrupts_ram_start__) : 0x0;
@@ -270,8 +277,10 @@ SECTIONS
     . = ALIGN(8);
     __end__ = .;
     PROVIDE(end = .);
+    __mbed_sbrk_start = .;
     __HeapBase = .;
     . = ORIGIN(m_data_2) + LENGTH(m_data_2) - STACK_SIZE;
+    __mbed_krbs_start = .;
     __HeapLimit = .;
     __heap_limit = .; /* Add for _sbrk */
   } > m_data_2

targets/targets.json

@@ -1489,7 +1489,7 @@
             "PSA"
         ],
         "is_disk_virtual": true,
-        "macros": ["CPU_MK64FN1M0VMD12", "FSL_RTOS_MBED"],
+        "macros": ["CPU_MK64FN1M0VMD12", "FSL_RTOS_MBED", "MBED_SPLIT_HEAP"],
         "inherits": ["Target"],
         "detect_code": ["0240"],
         "device_has": [
@@ -1777,7 +1777,7 @@
             "PSA"
         ],
         "is_disk_virtual": true,
-        "macros": ["CPU_MK66FN2M0VMD18", "FSL_RTOS_MBED"],
+        "macros": ["CPU_MK66FN2M0VMD18", "FSL_RTOS_MBED", "MBED_SPLIT_HEAP"],
         "inherits": ["Target"],
         "detect_code": ["0311"],
         "device_has": [