wifi: iwlegacy: do not skip frames with bad FCS

Monitor/sniffer mode benefits from all types of frames, even if FCS
check fails. But we must mark frames as such.

Tested on iwl3945 only.

Signed-off-by: Andrii Batyiev <batyiev@gmail.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240509101140.32664-1-batyiev@gmail.com