mac80211: do not access the IV when it was stripped

mac80211: do not access the IV when it was stripped

[ Upstream commit 77dfc2bc0bb4b8376ecd7a430f27a4a8fff6a5a0 ]

ieee80211_get_keyid() will return false value if IV has been stripped,
such as return 0 for IP/ARP frames due to LLC header, and return -EINVAL
for disassociation frames due to its length... etc. Don't try to access
it if it's not present.

Signed-off-by: Xing Song <xing.song@mediatek.com>
Link: https://lore.kernel.org/r/20211101024657.143026-1-xing.song@mediatek.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>