hv_netvsc: fix filter flags

[ Upstream commit de3d50aadd40bf68614db9fd157b275ce9c2d467 ]

The recent change to not always enable all multicast and broadcast
was broken; meant to set filter, not change flags.

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>