imx: mx6q/dlsabreauto: And NAND flash support

The i.MX6Q/DL sabreauto board has one NAND socket, set the
CONFIG_NAND_MXS and relevant NAND configurations to enable the
MXS NAND flash driver.
Add board level codes to set IOMUX and clock for GPMI-NAND and
BCH module.

Signed-off-by: Ye.Li <B37916@freescale.com>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>