bridge: Pseudo-header required for the checksum of ICMPv6

Checksum of ICMPv6 is not properly computed because the pseudo header is not used.
Thus, the MLD packet gets dropped by the bridge.

Signed-off-by: Zheng Yan <zheng.z.yan@intel.com>
Reported-by: Ang Way Chuang <wcang@sfc.wide.ad.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>