mac80211_hwsim: Advertise support for multicast RX registration

While mac80211_hwsim does not need this to configure RX filters, it is
convenient to have this enabled for testing purposes.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Link: https://lore.kernel.org/r/20200425155713.25687-3-jouni@codeaurora.org


Signed-off-by: Johannes Berg <johannes.berg@intel.com>