drm/msm: reset HDCP 2.2 sink support during disconnect

Reset the HDCP 2.2 sink support during a cable disconnect
to avoid stale information during the next cable connect.

This information is populated again from the sink on the next
cable connect.

Change-Id: I54da6e633915718da4be7023027c1d8c68cd6c21
Signed-off-by: Abhinav Kumar <abhinavk@codeaurora.org>