net/ipv6: remove unused err variable on icmpv6_push_pending_frames

int err is unused by icmpv6_push_pending_frames(), this patch returns removes the variable and returns the function with 0.

git bisect shows this variable has been around since linux has been in git in commit 1da177e4.

This was found by running make coccicheck M=net/ipv6/ on linus' tree on commit 77ede3a0

 (current HEAD as of this patch).

Signed-off-by: Tim Hansen <devtimhansen@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>