drm/sun4i: Don't change clock bits in DW HDMI PHY driver

DW HDMI PHY driver and PHY clock driver share same registers. Make sure
that DW HDMI PHY setup code doesn't change any clock related bits.
During initialization, set PHY PLL parent bit to 0.

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/20180625120304.7543-18-jernej.skrabec@siol.net