Merge branch 'ip6ip6-crash'

Daniel Borkmann says:

====================
Fix ip6ip6 crash for collect_md skbs

Fix a NULL pointer deref panic I ran into for regular ip6ip6 tunnel devices
when collect_md populated skbs were redirected to them for xmit. See patches
for further details, thanks!
====================

Signed-off-by: David S. Miller <davem@davemloft.net>