cfg80211: support multicast RX registration

For DPP, there's a need to receive multicast action frames,
but many drivers need a special filter configuration for this.

Support announcing from userspace in the management registration
that multicast RX is required, with an extended feature flag if
the driver handles this.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Sergey Matyukevich <sergey.matyukevich.os@quantenna.com>
Link: https://lore.kernel.org/r/20200417124013.c46238801048.Ib041d437ce0bff28a0c6d5dc915f68f1d8591002@changeid


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