msm: mdss: hdmi: fix uninitialized pointer issue in HDCP driver

Fix an issue related to an uninitialized pointer. Under certain
conditions, it is possible that the driver tries to free memory
whose reference is supposed to be held by this pointer and can
lead to a crash since the pointer doesn't hold a valid reference.

Change-Id: Ic2e16e1d67bc881bd2ae6d00a51ba12835c7a4f7
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>