r8152: allow userland to disable multicast

The rtl8152 driver does not disable multicasting when userspace asks
it to. For example:
$ ifconfig eth0 -multicast -allmulti
$ tcpdump -p -i eth0 # will still capture multicast frames

Fix by clearing the device multicast filter table when multicast and
allmulti are both unset.

Tested as follows:
- Set multicast on eth0 network interface
- verify that multicast packets are coming in:
$ tcpdump -p -i eth0
- Clear multicast and allmulti on eth0 network interface
- verify that no more multicast packets are coming in:
$ tcpdump -p -i eth0

Signed-off-by: Sven van Ashbrook <[e-mail]>
Acked-by: Hayes Wang <[e-mail]>
Link: https://lore.kernel.org/r/20220830045923.net-next.v1.1.I4fee0ac057083d4f848caf0fa3a9fd466fc374a0@changeid
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/usb/r8152.c

···
 		ocp_data |= RCR_AM | RCR_AAP;
 		mc_filter[1] = 0xffffffff;
 		mc_filter[0] = 0xffffffff;
-	} else if ((netdev_mc_count(netdev) > multicast_filter_limit) ||
-		   (netdev->flags & IFF_ALLMULTI)) {
+	} else if ((netdev->flags & IFF_MULTICAST &&
+				netdev_mc_count(netdev) > multicast_filter_limit) ||
+			   (netdev->flags & IFF_ALLMULTI)) {
 		/* Too many to filter perfectly -- accept all multicasts. */
 		ocp_data |= RCR_AM;
 		mc_filter[1] = 0xffffffff;
 		mc_filter[0] = 0xffffffff;
 	} else {
-		struct netdev_hw_addr *ha;
-
 		mc_filter[1] = 0;
 		mc_filter[0] = 0;
-		netdev_for_each_mc_addr(ha, netdev) {
-			int bit_nr = ether_crc(ETH_ALEN, ha->addr) >> 26;
 
-			mc_filter[bit_nr >> 5] |= 1 << (bit_nr & 31);
-			ocp_data |= RCR_AM;
+		if (netdev->flags & IFF_MULTICAST) {
+			struct netdev_hw_addr *ha;
+
+			netdev_for_each_mc_addr(ha, netdev) {
+				int bit_nr = ether_crc(ETH_ALEN, ha->addr) >> 26;
+
+				mc_filter[bit_nr >> 5] |= 1 << (bit_nr & 31);
+				ocp_data |= RCR_AM;
+			}
 		}
 	}