Fix minor uninitialized warnings from G++ 12.3.0

Use empty initializer list for struct clearing, avoiding a pedantic
warning from G++ 12 and 14.

Fixes #1785

Author: earlephilhower

src/rp2_common/hardware_pio/include/hardware/pio.h

@@ -647,7 +647,7 @@ static inline void sm_config_set_mov_status(pio_sm_config *c, enum pio_mov_statu
  * \return the default state machine configuration which can then be modified.
  */
 static inline pio_sm_config pio_get_default_sm_config(void) {
-    pio_sm_config c = {0};
+    pio_sm_config c = {};
 #if PICO_PIO_USE_GPIO_BASE
     c.pinhi = -1;
 #endif