u-boot-at91: enable u-boot-2014.07 for all avaliable boards

Signed-off-by: Josh Wu <josh.wu@atmel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
u-boot-at91: make at91sam9x5, sama5d3xek, sama5d3_xplained support v2014.07

Add the UBOOT_MACHINE in the machine files.

Signed-off-by: Josh Wu <josh.wu@atmel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>