rt2x00: Modify rt2x00queue_remove_l2pad to make skb->data two-byte alignment

When send out skb data to mac80211, orignal code will cause mac80211
unaligned access, so modify code to make mac80211 can natural access.

Signed-off-by: RA-Jay Hung <jay_hung@ralinktech.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>