wifi: mac80211: tx: use AP address in some places for MLO

In a few places we need to use the AP (MLD) address, not the
deflink BSSID, the link address translation will happen later.

To make that work properly for fast-xmit, set up the ap_addr
in the vif.cfg earlier.

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