Change keyboard level include guards to pragma once (#14248)

* Change keyboard level include guards to `pragma once`

And clean up a lot of layout macros

* Oops

* Remove dangling endif

keyboards/hhkb/rn42/rn42.h

@@ -1,5 +1,4 @@
-#ifndef RN42_H
-#define RN42_H
+#pragma once
 
 #include <stdbool.h>
 #include "host_driver.h"
@@ -26,5 +25,3 @@ void rn42_send_str(const char *str);
 void rn42_print_response(void);
 #define SEND_STR(str)       rn42_send_str(PSTR(str))
 #define SEND_COMMAND(cmd)   rn42_send_command(PSTR(cmd))
-
-#endif