drm/amd/display: add CRTC gamma TF driver-specific property

Add AMD pre-defined transfer function property to default DRM CRTC gamma
to convert to wire encoding with or without a user gamma LUT. There is
no post-blending regamma ROM for pre-defined TF. When setting Gamma TF
(!= Identity) and LUT at the same time, the color module will combine
the pre-defined TF and the custom LUT values into the LUT that's
actually programmed.

v2:
- enable CRTC prop in the end of driver-specific prop sequence
- define inverse EOTFs as supported regamma TFs
- reword driver-specific function doc to remove shaper/3D LUT

v3:
- spell out TF+LUT behavior in the commit and comments (Harry)

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Co-developed-by: Joshua Ashton <joshua@froggi.es>
Signed-off-by: Joshua Ashton <joshua@froggi.es>
Signed-off-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h

@@ -836,6 +836,14 @@ struct dm_crtc_state {
 	struct dc_info_packet vrr_infopacket;
 
 	int abm_level;
+
+        /**
+	 * @regamma_tf:
+	 *
+	 * Pre-defined transfer function for converting internal FB -> wire
+	 * encoding.
+	 */
+	enum amdgpu_transfer_function regamma_tf;
 };
 
 #define to_dm_crtc_state(x) container_of(x, struct dm_crtc_state, base)