iwlwifi: mvm: give client MACs time to synchronise during restart

When firmware restart happens, the timers are obviously reset and
the new firmware has no synchronisation with the AP as we program
timings to the pre-restart values. The firmware should attempt to
synchronise by itself, but in multi-channel scenarios this isn't
easy, particularly since it has to try to keep service quality up
for other MACs.

To make it more reliable, give each client MAC some time to catch
beacons when restarting or resuming. Service quality was impacted
anyway (or in resume doesn't really matter much.)

Reviewed-by: Moshe Island <moshe.island@intel.com>
Reviewed-by: Ilan Peer <ilan.peer@intel.com>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>