[bsp][nxp][frdm-mcxn236] fix SW btn

This is the SW2 button, a.k.a wakeup button on the board. Another
choice is SW3 a.k.a ISP button which is connected to P0_6.

bsp/nxp/mcx/mcxn/frdm-mcxn236/applications/main.c

@@ -17,7 +17,7 @@
 #include "drv_pin.h"
 
 #define LEDB_PIN        ((4*32)+18)
-#define BUTTON_PIN      ((0*32)+23)
+#define BUTTON_PIN      ((0*32)+20)
 
 static void sw_pin_cb(void *args);