wifi: iwlwifi: mvm: fix an error code in iwl_mvm_mld_add_sta()

This error path should return -EINVAL instead of success.

Fixes: 57974a55

 ("wifi: iwlwifi: mvm: refactor iwl_mvm_mac_sta_state_common()")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Acked-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/75e4ea09-db58-462f-bd4e-5ad4e5e5dcb5@moroto.mountain


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