Make default layer size 16-bit (#15286)

Co-authored-by: James Young <18669334+noroadsleft@users.noreply.github.com>

keyboards/maple_computing/lets_split_eh/keymaps/bbaserdem/keymap.c

@@ -5,7 +5,7 @@
 void matrix_init_keymap (void) {
 }
 
-uint32_t layer_state_set_keymap(uint32_t state) {
+layer_state_t layer_state_set_keymap(layer_state_t state) {
     return state;
 }
 

keyboards/maple_computing/lets_split_eh/keymaps/romus/keymap.c

@@ -5,8 +5,8 @@
 void matrix_init_keymap (void) {
 }
 
-uint32_t layer_state_set_keymap(uint32_t state) {
-	
+layer_state_t layer_state_set_keymap(layer_state_t state) {
+
     return state;
 }