msm_fb: HDMI: Reset HDCP reauth flag when powering off

The software flag used for storing the HDCP reauthentication state
needs to be reset whenever the HDMI device is powered off. This is
needed to avoid a potential reauthentication attempt upon a
subsequent connection which could lead to device hang as a result
of incorrect sequence of register accesses.

CRs-Fixed: 444312
Change-Id: I6b5b08394dd96ccbc08c4ca72b6dc4b2c4dbf6be
Signed-off-by: Aravind Venkateswaran <aravindh@codeaurora.org>