msm: clock-8960: Enable necessary regulators for hdmi_pll

Rather than requiring the display driver to enable these regulators
before enabling the clocks which use the HDMI PLL, enable these
regulators in the clock driver. The HDMI PLL is powered by the same
rail as the SR2 PLLs, so re-use that vdd_class.

Change-Id: Ieed938fc06cbd4ec7b6317b956b10d8ee7b4c578
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>