wifi: mwifiex: Fix oob check condition in mwifiex_process_rx_packet

Only skip the code path trying to access the rfc1042 headers when the
buffer is too small, so the driver can still process packets without
rfc1042 headers.

Fixes: 11958528 ("wifi: mwifiex: Fix OOB and integer underflow when rx packets")
Signed-off-by: Pin-yen Lin <treapking@chromium.org>
Acked-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Matthew Wang <matthewmwang@chromium.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230908104308.1546501-1-treapking@chromium.org