Some DW HDMI PHYs, like those found in A64 and R40 SoCs, can select
between two clock parents.

Add code which reads second PLL from DT.
Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180625120304.7543-19-jernej.skrabec@siol.net