ahci: added a new driver for supporting Freescale AHCI sata

Currently Freescale QorIQ series SATA is supported by ahci_platform
driver. Some SoC specific settings have been put in uboot. So whether
SATA works or not heavily depends on uboot.
This patch will add a new driver to support QorIQ sata which removes
the dependency on any other boot loader.
Freescale QorIQ series sata, like ls1021a ls2085a ls1043a, is
compatible with serial ATA 3.0 and AHCI 1.3 specification.

Signed-off-by: Yuantian Tang <Yuantian.Tang@freescale.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>