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

This reverts commit ec6bb01e which is
commit b0ec2abf98267f14d032102551581c833b0659d3 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: I8848ef10b837f2943ad2e56b56fd64d759558a81
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>