gpio-async: convert to ywf

Author: ppannuto

libtock-sync/peripherals/syscalls/gpio_async_syscalls.c

@@ -1,13 +1,13 @@
 #include "gpio_async_syscalls.h"
 
-yield_waitfor_return_t libtocksync_gpio_async_yield_wait_for_generic_command(void) {
+returncode_t libtocksync_gpio_async_yield_wait_for_generic_command(void) {
   yield_waitfor_return_t ret;
   ret = yield_wait_for(DRIVER_NUM_GPIO_ASYNC, 0);
 
   return (returncode_t) ret.data0;
 }
 
-yield_waitfor_return_t libtocksync_gpio_async_yield_wait_for_read(bool* value) {
+returncode_t libtocksync_gpio_async_yield_wait_for_read(bool* value) {
   yield_waitfor_return_t ywf;
   returncode_t ret;
 
@@ -17,4 +17,5 @@ yield_waitfor_return_t libtocksync_gpio_async_yield_wait_for_read(bool* value) {
   if (ret != RETURNCODE_SUCCESS) return ret;
 
   *value = (bool) ywf.data1;
+  return ret;
 }