icmpv6_filter: fix "_hdr" incorrectly being a pointer

"_hdr" should hold the ICMPv6 header while "hdr" is the pointer to it.
This worked by accident.

Signed-off-by: Werner Almesberger <werner@almesberger.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 file changed