LPC546XX: Do not make MCU_LPC546XX target public

This is a fix for Issue:9207

Signed-off-by: Mahesh Mahadevan <mahesh.mahadevan@nxp.com>

targets/targets.json

@@ -1961,6 +1961,7 @@
             "NXP_EMAC"
         ],
         "is_disk_virtual": true,
+        "public": false,
         "macros": ["CPU_LPC54628J512ET180", "FSL_RTOS_MBED"],
         "inherits": ["Target"],
         "device_has": [
@@ -7981,17 +7982,17 @@
         "device_has": [
             "ANALOGIN",
             "USTICKER",
-            "ANALOGOUT", 
-            "INTERRUPTIN", 
-            "PORTIN", 
-            "PORTINOUT", 
-            "PORTOUT", 
-            "PWMOUT", 
-            "SERIAL", 
-            "SLEEP", 
-            "SPI", 
-            "I2C", 
-            "I2CSLAVE", 
+            "ANALOGOUT",
+            "INTERRUPTIN",
+            "PORTIN",
+            "PORTINOUT",
+            "PORTOUT",
+            "PWMOUT",
+            "SERIAL",
+            "SLEEP",
+            "SPI",
+            "I2C",
+            "I2CSLAVE",
             "STDIO_MESSAGES",
             "MPU"
         ],