Define portNOP in RP2040 port (#1003)

Author: chinglee-iot

portable/ThirdParty/GCC/RP2040/include/portmacro.h

@@ -278,7 +278,7 @@ static inline void vPortRecursiveLock( uint32_t ulLockNum,
 #define portTASK_FUNCTION_PROTO( vFunction, pvParameters ) void vFunction( void * pvParameters )
 #define portTASK_FUNCTION( vFunction, pvParameters ) void vFunction( void * pvParameters )
 
-#define portNOP()
+#define portNOP() __asm volatile ( "nop" )
 
 #define portMEMORY_BARRIER() __asm volatile ( "" ::: "memory" )