nl80211: don't kfree() ERR_PTR() value

When parse_acl_data() fails, we get an ERR_PTR() value and
then "goto out;", in this case we'd attempt to kfree() it.
Fix that.

Fixes: 9e263e19 ("nl80211: don't put struct cfg80211_ap_settings on stack")
Link: https://lore.kernel.org/r/20210927134402.86c5ae06c952.Ic51e234d998b9045665e5ff8b6db7e29f25d70c0@changeid


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