wifi: mac80211: always free sta in __sta_info_alloc in case of error

Free sta pointer in __sta_info_alloc routine if sta_info_alloc_link()
fails.

Fixes: 246b39e4

 ("wifi: mac80211: refactor some sta_info link handling")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://lore.kernel.org/r/a3d079208684cddbc25289f7f7e0fed795b0cad4.1661260857.git.lorenzo@kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>