ARM64: dts: meson-axg: add AO clock driver

This add the AO (Always-On part) clock DT info for Meson-AXG SoC

Signed-off-by: Qiufang Dai <qiufang.dai@amlogic.com>
Signed-off-by: Yixun Lan <yixun.lan@amlogic.com>
[khilman: cleanup subject]
Signed-off-by: Kevin Hilman <khilman@baylibre.com>