wifi: iwlwifi: mvm: remove set_tim callback for MLD ops

In new firmware, we don't need this any more and it won't
be called any more by mac80211, since powersave handling
is all done by firmware. Remove it from the MLD ops.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20231017115047.1a1ded96ffc2.Ie49d3004acdd6299fb84346c76b2b2b2f195196b@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>