lan9118: fix multicast filtering

The lan9118 emulation tries to compute the multicast index by calling
directly the crc32() function from zlib, but fails to get the correct
result.

Use the common compute_mcast_idx() function instead, which gives the
correct result. This fixes IPv6 support.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
(cherry picked from commit 449bc90)

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

hw/lan9118.c

@@ -500,7 +500,7 @@ static int lan9118_filter(lan9118_state *s, const uint8_t *addr)
         }
     } else {
         /* Hash matching  */
-        hash = (crc32(~0, addr, 6) >> 26);
+        hash = compute_mcast_idx(addr);
         if (hash & 0x20) {
             return (s->mac_hashh >> (hash & 0x1f)) & 1;
         } else {