Merge branch 'Support-PMTU-in-tunnel-mode-for-packet-offload'

Leon Romanovsky says:

====================
This series refactors the xdo_dev_offload_ok() to be global place for
drivers to check if their offload can perform encryption for xmit
packets.

Such common place gives us an option to check MTU and PMTU at one place.
====================

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>