iwlwifi: mvm: set the MAC_FILTER_IN_BEACON flag also for P2P

There doesn't seem to be a good reason for not enabling the
MAC_FILTER_IN_BEACON flag for P2P client, as we do for station.

This can prevent potential, hard-to-reproduce problems during
association.

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