Define two structure mx6sl_iomux_ddr_regs and mx6sl_iomux_grp_regs.
Add a new function mx6sl_dram_iocfg to configure dram io.
Add header file to define macros for register address.
Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Cc: Stefano Babic <sbabic@denx.de>