sclk_hdmiphy clock is generated by HDMI-PHY and depends on hdmi gate clock.
The patch models this dependency using parent/child hirerarchy.

The patch fixes issue with system hangs during mixer device access, mixer uses
sclk_hdmiphy descendant clock.
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>