mtd: mxc_nand: add i.MX53 support

The only relevant change between i.MX51 and i.MX53 is that
a bitfield is shifted one bit to the left.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>