ARM: mx5: Add support for DENX M53EVK

This patch adds support for the DENX M53EVK board. The board currently supports
NAND, Ethernet, UART, CAN, I2C.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>