If the deflink of the station is on 6 GHz, then it won't have HT.
If at the same time we're using MLO, then vif.bss_conf isn't used,
and thus vif.bss_conf.chandef.chan is NULL, causing the code to
crash.

Fix this by just checking for both HT and HE, and refusing the
aggregation session if both are not present. This might be a bit
wrong since it would accept an aggregation session from a peer
that has HE but no HT on 2.4 or 5 GHz, but such a peer shouldn't
exist in the first place, and it probably supports aggregation if
it has HE support.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>