staging: r8188eu: clean up rtw_rf.c

Remove unnecessary includes and the unused define _RTW_RF_C_ from
rtw_rf.c.
Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20220222082847.6687-4-straube.linux@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/r8188eu/core/rtw_rf.c

 // SPDX-License-Identifier: GPL-2.0
 /* Copyright(c) 2007 - 2011 Realtek Corporation. */
 
-#define _RTW_RF_C_
-
-#include "../include/osdep_service.h"
 #include "../include/drv_types.h"
-#include "../include/recv_osdep.h"
-#include "../include/xmit_osdep.h"
 
 static const u32 ch_freq_map[] = {
 	2412,