staging: r8188eu: fix array_size.cocci warning

Fix following array_size.cocci warning:
./drivers/staging/r8188eu/core/rtw_rf.c:38:48-49: WARNING: Use ARRAY_SIZE.

ARRAY_SIZE() defined in <linux/kernel.h> is safer because it uses
__must_be_array().

Signed-off-by: Guo Zhengkui <guozhengkui@vivo.com>
Link: https://lore.kernel.org/r/20211116064124.8833-2-guozhengkui@vivo.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>