ata: sata_mv: introduce compatible string "marvell, armada-370-sata"

The sata_mv driver supports the SATA IP found in several Marvell SoCs.
As some new SATA registers have been introduced with the Armada 370/XP
SoCs, a way to identify them is needed.

This patch introduces a new compatible string for the SATA IP found in
Armada 370/XP SoCs.

Signed-off-by: Simon Guinot <simon.guinot@sequanux.org>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Gregory Clement <gregory.clement@free-electrons.com>
Cc: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Cc: Lior Amsalem <alior@marvell.com>
Cc: stable@vger.kernel.org # v3.6+
Acked-by: Jason Cooper <jason@lakedaemon.net>
Signed-off-by: Tejun Heo <tj@kernel.org>