iwlwifi: mvm: fix GO powersave client manipulation

All station commands must include a valid MAC ID,
the ID 0 is randomly valid in some cases, but we
must set the ID properly. Do that by passing the
right station and using its mac_id_n_color.

Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>