driver: ddr: fsl_mmdc: Pass board parameters through data structure

driver: ddr: fsl_mmdc: Pass board parameters through data structure

Instead of using multiple macros, a data structure is used to pass
board-specific parameters to MMDC DDR driver.

Signed-off-by: York Sun <york.sun@nxp.com>
CC: Shengzhou Liu <Shengzhou.Liu@nxp.com>
Reviewed-by: Tom Rini <trini@konsulko.com>