staging: rtl8188eu: constify some arrays

The values of these arrays in rtw_mlme_ext.c and rtw_wlan_util.c
are never changed, so make them const.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>