[PATCH] drivers/net/wireless/libertas/rx.c: fix use-after-free

skb could have been freed by then. Also, in libertas_upload_rx_packet(),
skb->protocol is initialized by eth_type_trans().

Signed-off-by: Eugene Teo <eugeneteo@kernel.sg>
Signed-off-by: John W. Linville <linville@tuxdriver.com>