Revert "ipip,ip_tunnel,sit: Add FOU support for externally controlled ipip devices"

This reverts commit 19bbca7b which is
commit ac931d4c upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I5257d2983050a26af2c599f91eee7af6d6141c9d
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>