msm: clock-8974: Add support for HDMI PHY PLL control through clock driver.

The hdmi phy pll drives the HDMI PHY as well as extpclk required by
hdmi tx controller. Add support to control this pll through clock
driver apis.

Change-Id: I851c586a14afda5b4079f850a3161518bee5af4a
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>