Reverse the logic to get_interrupts_disabled() to are_interrupts_enabled()

and update the using functions accordingly.

Usage:
bool interrupts_enabled = are_interrupts_enabled()

Remove superfluos shift in are_interrupts_enabled().

hal/api/critical.h

@@ -25,16 +25,16 @@ extern "C" {
 #endif
 
 
-/** Determine the current interrupts disabled state
+/** Determine the current interrupts enabled state
   *
-  * This function can be called to determine whether or not interrupts are currently disabled.
+  * This function can be called to determine whether or not interrupts are currently enabled.
   * \note
   * NOTE:
   * This function works for both cortex-A and cortex-M, although the underlyng implementation
   * differs.
-  * @return true if interrupts are disabled, false otherwise
+  * @return true if interrupts are enabled, false otherwise
   */
-bool get_interrupts_disabled(void);
+bool are_interrupts_enabled(void);
 
 /** Mark the start of a critical section
   *

hal/common/critical.c

@@ -29,19 +29,18 @@
 static volatile uint32_t interrupt_enable_counter = 0;
 static volatile bool critical_interrupts_disabled = false;
 
-bool get_interrupts_disabled(void)
+bool are_interrupts_enabled(void)
 {
 #if defined(__CORTEX_A9)
-    bool interrupts_disabled = (bool)(((__get_CPSR() & 0x80) >> 7) & 0x1);
+    return ((__get_CPSR() & 0x80) == 0);
 #else
-    bool interrupts_disabled = (bool)(__get_PRIMASK() & 0x1);
+    return ((__get_PRIMASK() & 0x1) == 0);
 #endif
-    return interrupts_disabled;
 }
 
 void core_util_critical_section_enter()
 {
-    bool interrupts_disabled = get_interrupts_disabled();
+    bool interrupts_disabled = !are_interrupts_enabled();
     __disable_irq();
 
     /* Save the interrupt disabled state as it was prior to any nested critical section lock use */
@@ -71,7 +70,7 @@ void core_util_critical_section_exit()
 
 // FIXME
 #ifndef   FEATURE_UVISOR
-        bool interrupts_disabled = get_interrupts_disabled(); /* get the current interrupt disabled state */
+        bool interrupts_disabled = !are_interrupts_enabled(); /* get the current interrupt disabled state */
 
         MBED_ASSERT(interrupts_disabled); /* Interrupts must be disabled on invoking an exit from a critical section */
 #else