staging: rtl8723au: core: rtw_mlme: fix void function return statements

The following patch fixes the checkpatch.pl warning:

drivers/staging/rtl8723au/core/rtw_mlme.c WARNING: void function return statements are not generally useful

Signed-off-by: Yeliz Taneroglu <yeliztaneroglu@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>