arm: mvebu: serdes: Move Armada XP SERDES / PHY init code into new directory

arm: mvebu: serdes: Move Armada XP SERDES / PHY init code into new directory

With the upcoming addition of the Armada 38x SPL support, which is not
compatible to the Armada XP SERDES init code, we need to introduce a new
directory infrastructure. So lets move the AXP serdes init code into
a new directory. This way the A38x code can be added in a clean way.

Signed-off-by: Stefan Roese <sr@denx.de>