SATA: add driver for MX5 / MX6 SOCs

This driver is part of Freescale's LTIB for
MX5 / MX6.

Signed-off-by: Stefano Babic <sbabic@denx.de>
Signed-off-by: Terry Lv <r65388@freescale.com>
CC: Fabio Estevam <fabio.estevam@freescale.com>
CC: Dirk Behme <dirk.behme@de.bosch.com>