sata: sata_mv: Add DM support to enable CONFIG_BLK usage

sata: sata_mv: Add DM support to enable CONFIG_BLK usage

This patch adds DM support to the Armada XP SATA driver. This is needed
to enable CONFIG_BLK on this platform. It adds the SATA controller as
AHCI device, which is strictly speaking not correct, as the controller
is not AHCI compatible. But the U-Boot AHCI uclass interface enables
the usage of this DM driver and the creation of the corresponding BLK
devices.

This conversion is done to get rid of the compile warning:
Reviewed-by: Chris Packham <judge.packham@gmail.com>
===================== WARNING ======================
This board does not use CONFIG_DM_SCSI. Please update
the storage controller to use CONFIG_DM_SCSI before the v2019.07 release.
Failure to update by the deadline may result in board removal.
See doc/driver-model/MIGRATION.txt for more info.
====================================================

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@konsulko.com>