Merge branch 'geneve-mtu'

Alexey Kodanev says:

====================
geneve: verify user specified MTU or adjust with a lower device

The first two patches don't introduce any functional changes and
contain minor cleanups for code readability.

The last one adds a new function geneve_link_config() similar to the
other tunnels. The function will be used on a new link creation or
when 'remote' parameter is changed. It adjusts a user specified MTU
or, if it finds a lower device, tunes the tunnel MTU using it.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>