fsl

This general MMDC driver adds basic support for Freescale MMDC
(Multi Mode DDR Controller). Currently MMDC is integrated on ARMv8
LS1012A SoC for DDR3L, there will be a update to this driver to
support more flexible configuration if new features (DDR4, multiple
controllers/chip selections, etc) are implimented in future.

Meantime, reuse common MMDC driver for LS1012ARDB/LS1012AQDS/
LS1012AFRDM.

Signed-off-by: Shengzhou Liu <Shengzhou.Liu@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>