wifi: mac80211: mlme: fix memory leak

When re-parsing the elements here (with changed mode), free
the original ones first to avoid leaking memory.

Fixes: 310c8387

 ("wifi: mac80211: clean up connection process")
Reviewed-by: Miriam Rachel Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20240418105220.458421e3bbff.Icb5b84cba3ea420794cf009cf18ec3d76e434736@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>