Change include guards in tmk_core/ and drivers/ to pragma once (#11240)

tmk_core/protocol/chibios/usb_main.h

@@ -15,8 +15,7 @@
  * GPL v2 or later.
  */
 
-#ifndef _USB_MAIN_H_
-#define _USB_MAIN_H_
+#pragma once
 
 // TESTING
 // extern uint8_t blinkLed;
@@ -89,5 +88,3 @@ int8_t sendchar(uint8_t c);
 void console_flush_output(void);
 
 #endif /* CONSOLE_ENABLE */
-
-#endif /* _USB_MAIN_H_ */