wifi: mac80211: fix link warning in RX agg timer expiry

The rx data link pointer isn't set from the RX aggregation timer,
resulting in a later warning. Fix that by setting it to the first
valid link for now, with a FIXME to worry about statistics later,
it's not very important since it's just the timeout case.

Reported-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/498d714c-76be-9d04-26db-a1206878de5e@redhat.com


Fixes: 56057da4 ("wifi: mac80211: rx: track link in RX data")
Signed-off-by: Mukesh Sisodiya <mukesh.sisodiya@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>