reset: meson-axg: add compatible string for Meson-AXG SoC

Try to add compatible string explictly to support new Meson-AXG SoC.

Signed-off-by: Yixun Lan <yixun.lan@amlogic.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>