imx: mx53ard: Add support for NAND Flash

Add support for the Samsung K9LAG08U0M NAND Flash (2-GiB MLC NAND Flash, 2-kiB
pages, 256-kiB blocks, 30-ns R/W cycles, 1 CS) on mx53ard.

eNFC_CLK_ROOT is set up with a cycle time of 37.5 ns (400 MHz / 3 / 5) for this
board, which satisfies the 30-ns NF R/W cycle requirement.

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>