iwlwifi: mvm: update station when marked associated

In managed mode, the HT/VHT capabilities aren't set when
the station is initially added, so update the station
when it is marked associated. In AP/GO mode, the station
will typically be added with full capabilities today,
but an upcoming change in hostapd may mean a similar
scenario as for managed mode, therefore do the update
unconditionally.

Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>