staging: rtl8723bs: remove unused variable in os_dep/ioctl_linux.c

staging: rtl8723bs: remove unused variable in os_dep/ioctl_linux.c

fix following kernel test robot warning:

drivers/staging/rtl8723bs/os_dep/ioctl_linux.c:
In function ‘rtw_wx_set_mlme’:
drivers/staging/rtl8723bs/os_dep/ioctl_linux.c:1128:6:
warning: variable ‘reason’ set but
	not used [-Wunused-but-set-variable]
  u16 reason;
      ^~~~~~

Signed-off-by: Fabio Aiuto <fabioaiuto83@gmail.com>
Link: https://lore.kernel.org/r/6211c4177a9ef1e677987c9ebac445df08605f40.1617962215.git.fabioaiuto83@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>