Revert "ipv6: save dontfrag in cork"

Revert "ipv6: save dontfrag in cork"

This reverts commit 2b572c40981138349c04b3f69220ac878a36c561 which is
commit a18dfa9925b9ef6107ea3aa5814ca3c704d34a8a upstream.

A regression was introduced when backporting this to the stable kernels
without applying previous commits in this series.

When sending IPv6 UDP packets larger than MTU, EMSGSIZE was returned
instead of fragmenting the packets as expected.

As there is no compelling reason for this commit to be present in the
stable kernels it should be reverted.

Signed-off-by: Brett A C Sheffield <bacs@librecast.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>