staging: rtl8723au: Make rtw_get_capability23a_from_ie() return __le 16 *

This should make sparse happier.

Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>