ahci: added support for Freescale AHCI sata

Freescale introduced QorIQ series SOCs, like ls1021 ls2085, with AHCI
sata support. It complies with the serial ATA 3.0 specification
and the AHCI 1.3 specification.

Signed-off-by: Shaohui Xie <Shaohui.Xie@freescale.com>
Signed-off-by: Yuantian Tang <Yuantian.Tang@freescale.com>
Signed-off-by: Tejun Heo <tj@kernel.org>