machine: use armv8-a, not armv8
machine: use armv8-a, not armv8

In the latest OE, this file has been renamed. Since this board is
ARMv8-A, we should use the armv8-a config instead of the armv8 config.

Signed-off-by: Martin Kelly <c87c89f8a4ed3f9815bf6eb199372979d459c1c8@xevo.com>

net147/meta-sunxi,twoerner/meta-sunxi,linux-sunxi/meta-sunxi,linux-sunxi/meta-sunxi,net147/meta-sunxi,linux-sunxi/meta-sunxi,twoerner/meta-sunxi