Staging: rt3090: port changes in WPA_MIX_PAIR_CIPHER to rt3090

This patch ports a change recently applied to rt2860/rt2870 in order to
change handling of WPA1/WPA2 mixed mode to rt3090.

Signed-off-by: Axel Koellhofer <rain_maker@root-forum.org>
Acked-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>