drm/amd/display: Handle Content protection property changes

[Why]
We need to manage the content protection property changes for
different usecase, once cp is DESIRED we need to maintain the
ENABLED/DESIRED status for different cases.

[How]
1. Attach the content_protection property

2. HDCP enable (UNDESIRED -> DESIRED)
	call into the module with the correct parameters to start
	hdcp. Set cp to ENABLED

3. HDCP disable (ENABLED -> UNDESIRED)
	Call the module to disable hdcp.

3. Handle Special cases	(Hotplug, S3, headless S3, DPMS)
	If already ENABLED: set to DESIRED on unplug/suspend/dpms,
	and disable hdcp

	Then on plugin/resume/dpms: enable HDCP

Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>