wifi: iwlwifi: mvm: check for iwl_mvm_mld_update_sta() errors

The return value of this function is assigned, but then unused.
Check for errors here.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230921110727.a9496c232d48.I74adaa8f3c6fd3252348e79f18605246936ef27d@changeid


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