drm: Add Content protection type property

This patch adds a DRM ENUM property to the selected connectors.
This property is used for mentioning the protected content's type
from userspace to kernel HDCP authentication.

Type of the stream is decided by the protected content providers.
Type 0 content can be rendered on any HDCP protected display wires.
But Type 1 content can be rendered only on HDCP2.2 protected paths.

So when a userspace sets this property to Type 1 and starts the HDCP
enable, kernel will honour it only if HDCP2.2 authentication is through
for type 1. Else HDCP enable will be failed.

Pekka have completed the Weston DRM-backend review in
https://gitlab.freedesktop.org/wayland/weston/merge_requests/48


and the UAPI for HDCP 2.2 looks good.

The userspace is accepted in Weston.

v2:
  cp_content_type is replaced with content_protection_type [daniel]
  check at atomic_set_property is removed [Maarten]
v3:
  %s/content_protection_type/hdcp_content_type [Pekka]
v4:
  property is created for the first requested connector and then reused.
	[Danvet]
v5:
  kernel doc nits addressed [Daniel]
  Rebased as part of patch reordering.
v6:
  Kernel docs are modified [pekka]
v7:
  More details in Kernel docs. [pekka]
v8:
  Few more clarification into kernel doc of content type [pekka]
v9:
  Small fixes in coding style.
v10:
  Moving DRM_MODE_HDCP_CONTENT_TYPEx definition to drm_hdcp.h [pekka]

Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/320957/?series=57232&rev=14