wifi: cfg80211: report per-link errors during association

wifi: cfg80211: report per-link errors during association

When one of the links (other than the assoc_link) is misconfigured
and cannot work the association will fail. However, userspace was not
able to tell that the operation only failed because of a problem with
one of the links. Fix this, by allowing the driver to set a per-link
error code and reporting the (first) offending link by setting the
bad_attr accordingly.

This only allows us to report the first error, but that is sufficient
for userspace to e.g. remove the offending link and retry.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230920211508.ebe63c0bd513.I40799998f02bf987acee1501a2522dc98bb6eb5a@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>