wifi: iwlwifi: mvm: Handle return value for iwl_mvm_sta_init

sta_init function can fail and if it returns an error then
driver should not send the request to fw to add a station.

Fixes: 69aef848 ("wifi: iwlwifi: mvm: refactor iwl_mvm_add_sta(), iwl_mvm_rm_sta()")
Signed-off-by: Mukesh Sisodiya <mukesh.sisodiya@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230612184434.1ecd293539e8.I5ec6aab387bb2fe743a7402581beaeb9c801d31f@changeid


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