hv_netvsc: enable multicast if necessary

hv_netvsc: enable multicast if necessary

[ Upstream commit f03dbb06dc380274e351ca4b1ee1587ed4529e62 ]

My recent change to netvsc drive in how receive flags are handled
broke multicast.  The Hyper-v/Azure virtual interface there is not a
multicast filter list, filtering is only all or none. The driver must
enable all multicast if any multicast address is present.

Fixes: 009f766ca238 ("hv_netvsc: filter multicast/broadcast")
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>