Revert "net: ip_tunnel: make sure to pull inner header in ip_tunnel_rcv()"

This reverts commit 77fd5294 which is
commit b0ec2abf 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: I481b44d90e063818b1b6ed83ec319862c705531d
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>