ipv6: Make MLD packets to only be processed locally

Before commit daad1512 ("ipv6: Make ipv6_is_mld() inline and use it
from ip6_mc_input().") MLD packets were only processed locally. After the
change, a copy of MLD packet goes through ip6_mr_input, causing
MRT6MSG_NOCACHE message to be generated to user space.

Make MLD packet only processed locally.

Fixes: daad1512 ("ipv6: Make ipv6_is_mld() inline and use it from ip6_mc_input().")
Signed-off-by: Hermin Anggawijaya <hermin.anggawijaya@alliedtelesis.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>