msm: mdss: hdmi: remove DDC power disable in HPD off

The HDMI driver is causing an unbalanced
mdss_update_reg_bus_vote call when powering off HPD
in suspend state. Since the DDC module is powered
on for HDCP in MDSS_EVENT_PANEL_ON and then powered
off in MDSS_EVENT_BLANK, there is no need to power
off the DDC module again in the HPD off function.

Change-Id: I3b5e9e352d07e572e6c909554945d949fc374287
Signed-off-by: Casey Piper <cpiper@codeaurora.org>