arm: ls102xa: Add basic support for LS1021AQDS board

LS102xA is an ARMv7 implementation. This patch is to add
basic support for LS1021AQDS board.
 One DDR controller
 DUART1 is used as the console

For the detail board information, please refer to README.

Signed-off-by: Alison Wang <alison.wang@freescale.com>
Signed-off-by: Jason Jin <jason.jin@freescale.com>
Signed-off-by: York Sun <yorksun@freescale.com>
Signed-off-by: Yuan Yao <yao.yuan@freescale.com>
Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>