net: remove unused compute_mcast_idx() function

Now that all of the callers have been converted to compute the multicast index
inline using new net CRC functions, this function can now be dropped.
Signed-off-by: NMark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: NJason Wang <jasowang@redhat.com>

net/net.c

@@ -1625,11 +1625,6 @@ uint32_t net_crc32_le(const uint8_t *p, int len)
     return crc;
 }
 
-unsigned compute_mcast_idx(const uint8_t *ep)
-{
-    return net_crc32(ep, ETH_ALEN) >> 26;
-}
-
 QemuOptsList qemu_netdev_opts = {
     .name = "netdev",
     .implied_opt_name = "type",