clk: qcom: mdss: add PLL clock support for 20nm HDMI PHY

Add support for HDMI PLL on msm8994.
Support is added to register this new clock
driver. Also modify makefile to compile new
20nm PLL source and add support for registering
PLL clock driver for 20nm HDMI PHY.

Change-Id: I57421ac638075358c46ddd938e441a8e525f3a5a
Signed-off-by: Casey Piper <cpiper@codeaurora.org>