ARM: dts: Add initial LS1021A TWR board dts support

The LS1021A TWR is a low cost, high-performance evaluation,
development and test platform supporting the LS1021A processor.
It is optimized to support the high-bandwidth DDR3L memory and
a full complement of high-speed SerDes ports.

For more detail information about the LS1021A TWR board, please
refer to LS1021A QorIQ Tower System Reference Manual.

Signed-off-by: Chao Fu <B44548@freescale.com>
Signed-off-by: Jingchang Lu <jingchang.lu@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>