ESP32: Use __asm__ __volatile__ for inline assembly

arch/xtensa/src/common/xtensa_idle.c

@@ -98,5 +98,5 @@ void up_idle(void)
    * sleep in a reduced power mode until an interrupt occurs to save power
    */
 
-  asm("waiti 0");
+  __asm__ __volatile__ ("waiti 0");
 }

arch/xtensa/src/esp32/esp32_cpustart.c

@@ -195,7 +195,7 @@ void xtensa_appcpu_start(void)
 
   /* Move CPU0 exception vectors to IRAM */
 
-  asm volatile ("wsr %0, vecbase\n"::"r" (&_init_start));
+  __asm__ __volatile__ ("wsr %0, vecbase\n"::"r" (&_init_start));
 
   /* Make page 0 access raise an exception */
 

arch/xtensa/src/esp32/esp32_start.c

@@ -124,7 +124,7 @@ void IRAM_ATTR __start(void)
 
   /* Move CPU0 exception vectors to IRAM */
 
-  asm volatile ("wsr %0, vecbase\n"::"r" (&_init_start));
+  __asm__ __volatile__ ("wsr %0, vecbase\n"::"r" (&_init_start));
 
   /* Set .bss to zero */