ARM64: dts: meson-gx: sysctrl is the parent of the clock controller

The parent of the meson-gx clock controller should be the hhi system
controller, not the HIU bus. This way, the HHI register region can be
used safely by multiple drivers

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>