wifi: mac80211: reject WEP or pairwise keys with key ID > 3

We don't really care too much right now since our data
structures are set up to not have a problem with this,
but clearly it's wrong to accept WEP and pairwise keys
with key ID > 3.

However, with MLD we need to split into per-link (GTK,
IGTK, BIGTK) and per interface/MLD (including WEP) keys
so make sure this is not a problem.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>