drm/msm/hdmi: Manage HDMI PLL through PHY driver

Add a helper to initialize PLL in the PHY driver. HDMI PLLs are going to
have their own mmio base different from that of PHY.

For the clock code in hdmi_phy_8960.c, some changes were needed for it to
work with the updated register offsets. Create a copy of the updated clock
code in hdmi_pll_8960.c, instead of rewriting it in hdmi_phy_8960.c
itself. This removes the need to place CONFIG_COMMON_CLOCK checks all
around, makes the code more legible, and also removes some old checkpatch
warnings with the original code.

The older hdmi pll clock ops in hdmi_phy_8960.c will be removed later. The
driver will use these until the HDMI PHY/PLL register offsets aren't
considered as separate domains (i.e. their offsets start from 0).

Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>