mwifiex: add a bounds check in mwifiex_process_sta_rx_packet()

mwifiex: add a bounds check in mwifiex_process_sta_rx_packet()

Smatch complains that "local_rx_pd->priority" can't be trusted because
it comes from skb->data and it can go up to 255 instead of being capped
in the 0-7 range.  A few lines earlier, on the other side of the if
statement, we cap priority so it seems harmless to add a bounds check
here as well.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>