wifi: mac80211: check defragmentation succeeded

We need to check that cfg80211_defragment_element()
didn't return an error, since it can fail due to bad
input, and we didn't catch that before.

Fixes: 8eb8dd2f ("wifi: mac80211: Support link removal using Reconfiguration ML element")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20231211085121.8595a6b67fc0.I1225edd8f98355e007f96502e358e476c7971d8c@changeid


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