aarch64: add initial support

Add initial support for the AArch64 architecture

Signed-off-by: Florian Fainelli <florian@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@43353 3c298f89-4303-0410-b956-a3cf2f4a3e73
libbsd: add support for aarch64

Signed-off-by: Florian Fainelli <florian@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@43354 3c298f89-4303-0410-b956-a3cf2f4a3e73
arm64: add ARM 64-bits target

This target can be emulated using ARM's Foundation_V8 simulator
software or qemu-system-aarch64 using the command-line described in the
README file.

Signed-off-by: Florian Fainelli <florian@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@43355 3c298f89-4303-0410-b956-a3cf2f4a3e73