Remove hardware dependence in portmacros.h

The IAR MSP430X port `#include "msp430.h"` which pulls all the hardware
register definitions into anything which `#include "FreeRTOS.h"`.  This
removes that hardware dependency "leak" by removing the header file
and re-defining the `portDISABLE_INTERRUPTS()` and
`portENABLE_INTERRUPTS()` macros in terms of `__asm`.

portable/IAR/MSP430X/portmacro.h

@@ -39,9 +39,6 @@
  *-----------------------------------------------------------
  */
 
-/* Hardware includes. */
-#include "msp430.h"
-
 /* Type definitions. */
 #define portCHAR         char
 #define portFLOAT        float
@@ -75,8 +72,8 @@ typedef unsigned short   UBaseType_t;
 /*-----------------------------------------------------------*/
 
 /* Interrupt control macros. */
-#define portDISABLE_INTERRUPTS()    _DINT(); _NOP()
-#define portENABLE_INTERRUPTS()     _EINT(); _NOP()
+#define portDISABLE_INTERRUPTS()    __asm volatile ( "DINT\n" "NOP")
+#define portENABLE_INTERRUPTS()     __asm volatile ( "EINT\n" "NOP")
 /*-----------------------------------------------------------*/
 
 /* Critical section control macros. */