mac80211: fix fast-rx encryption check

stable inclusion
from stable-5.10.14
commit 20790b2534f2057345ffd75e77c9758e4d94407e
bugzilla: 48051

--------------------------------

[ Upstream commit 622d3b4e ]

When using WEP, the default unicast key needs to be selected, instead of
the STA PTK.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Link: https://lore.kernel.org/r/20201218184718.93650-5-nbd@nbd.name


Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>