kernel: add some missing config symbols

Signed-off-by: Florian Fainelli <florian@openwrt.org>
aarch64: add initial support

Add initial support for the AArch64 architecture

Signed-off-by: Florian Fainelli <florian@openwrt.org>
libbsd: add support for aarch64

Signed-off-by: Florian Fainelli <florian@openwrt.org>
fvp: add Versatile Express V8 Foundation target

This target can be emulated using ARM's Foundation_V8 simulator
software.

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