iwlwifi: mvm: Do not sample the device time for session protection

Since the time-event is sent with the immediate flag set, there is
no need to sample the device time.

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