Add a subtarget for Atmel's SAMA5D3 Cortex-A5 based SoCs. Signed-off-by: Florian Fainelli <florian@openwrt.org> git-svn-id: svn://svn.openwrt.org/openwrt/trunk@42417 3c298f89-4303-0410-b956-a3cf2f4a3e73