wl1271: avoid redundant memcpy of rx_status

copy the rx_status directly to skb->cb (control buffer) instead of copying
it to a local struct and then copying it again (for each rx packet)

Signed-off-by: Eliad Peller <eliad@wizery.com>
Acked-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>