ata: ahci: Add SATA support for Qualcomm MSM chipsets

Add a glue driver for AHCI platform driver to support SATA
controller and PHY on Qualcomm's MSM platforms. The SATA
controller on MSM adheres to AHCI 1.3 specification and SATA
PHY is based on SATA 3.0 specification.

The glue driver acts as a device driver for msm_sata device and
registers AHCI device in its probe, AHCI platform driver then
acts as a device driver for created AHCI device. All the necessary
msm platform specific initialization is handled by msm_sata driver
while keeping ahci_platform generic enough.

Following are done during controller initialization:
 - SATA clocks initialization.
 - SATA regulator initialization.
 - SATA PHY calibration.

Change-Id: I3e36289992c340bc16fcb2a6c52468cc95679fe8
Signed-off-by: Sujit Reddy Thumma <sthumma@codeaurora.org>
Signed-off-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>