conf/machine: add support for rk1808
conf/machine: add support for rk1808

RK1808 is an ARM processor with a neural network process unit,
which can acceleration the inference of deep learning.

Signed-off-by: Randy Li <956d2c7ac7b6029589e6f6a018fbbf7b58c05b23@rock-chips.com>

hizukiayaka/meta-rockchip,hizukiayaka/meta-rockchip,hizukiayaka/meta-rockchip