msm: mdss: add HDCP 2.2 driver support for encryption level

When an application requests a particular minimum
HDCP encryption level, the kernel exposes an API
that informs the HDCP library of this change.
Add support for this API call.

Change-Id: I508a08f946c8d36a2567f3e7fba2e5b01e992e31
Signed-off-by: Casey Piper <cpiper@codeaurora.org>