wifi: mac80211: make associated BSS pointer visible to the driver

Some drivers need the data in it, so move it to the link conf,
which is exposed to the driver.

Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20240206164849.6fe9782b87b4.Ifbffef638f07ca7f5c2b27f40d2cf2942d21de0b@changeid


[remove bss pointer from internal struct, update docs]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>