Merge branch 'Add-5gbase-r-PHY-interface-mode'

Marek Behún says:

====================-
Add 5gbase-r PHY interface mode

there is still some testing needed for Amethyst patches, so I have
split the part adding support for 5gbase-r interface mode and am sending
it alone.

The first two patches are already reviewed.

Changes since last patches (Amethyst v16):
- added phylink 5gbase-r handler
- added SFP support for 5gbase-r mode
====================

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