arm64: configs: Enable Actions Semi platform in defconfig

Since there are enough consumers (drivers) for Actions Semi platform in
mainline, let's enable it in ARM64 defconfig. As of now, this platform
can boot a distro from eMMC/uSD.

Link: https://lore.kernel.org/r/20191015152204.5610-1-manivannan.sadhasivam@linaro.org


Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>