disp: hdcp: add driver to handle userspace interactions

Create a new driver to handle sysfs and topology events that are
related to application/userspace layer interactions for HDCP
functionality. In turn, this will create a clear separation from
the HDCP QSEECOM layer that defines the communication mechanism
between the kernel and the TrustZone layers.

This implementation is based on a snapshot of the msm_hdcp
driver as of this commit 10ffbfa2c7e03c09 ("drm/msm/dp: Snapshot
of DP and supporting files") on kernel 4.19 project.

Change-Id: I834620420b8d6a580f1905a2b3250cf4e5b8f293
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>