arm: mvebu: SATA support: board-level DT data for Armada 370/XP boards

Add the SATA device tree bindings for
- Armada XP evaluation board (DB-78460-BP)
- Armada 370 evaluation board (DB-88F6710-BP-DDR3)

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Lior Amsalem <alior@marvell.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>