wifi: mac80211: fix unaligned le16 access

The AP removal timer field need not be aligned, so the
code shouldn't access it directly, but use unaligned
loads. Use get_unaligned_le16(), which even is shorter
than the current code since it doesn't need a cast.

Fixes: 8eb8dd2f

 ("wifi: mac80211: Support link removal using Reconfiguration ML element")
Reviewed-by: Ilan Peer <ilan.peer@intel.com>
Reviewed-by: Miriam Rachel Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20240418105220.356788ba0045.I2b3cdb3644e205d5bb10322c345c0499171cf5d2@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>