ahci: sata: add support for exynos5440 sata

This patch adds the compatible string of the exynos5440 sata controller
compliant with the ahci 1.3 and sata 3.0 specification.

changes in v2:
		changed the compatible string by adding the actual IP
owners name instead of the SoC vendor name.

Signed-off-by: Girish K S <ks.giri@samsung.com>
Signed-off-by: Tejun Heo <tj@kernel.org>