Staging: rt28x0: Add proper selection of WIRELESS_EXT and WEXT_PRIV

After the incorporation of the patch entitled "wext: refactor", some
of the wireless drivers in drivers/staging fail to build because they
need to have CONFIG_WIRELESS_EXT and CONFIG_WEXT_PRIV defined.

[ patch description borrowed from the previous fix for wireless staging
  drivers ("staging: Add proper selection of WIRELESS_EXT and WEXT_PRIV")
  authored by Larry Finger ]

Cc: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>