Config System: Add support for android configuration item

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Android: automatically set command line when loading android image

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
defconfig: update the sama5d3xek default configuration file for loading android image

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>