drm/amd/display: set sdr_ref_white_level to 80 for out_transfer_func

Otherwise this is just initialized to 0. This needs to actually have a
value so that compute_curve can work for PQ EOTF.
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Joshua Ashton <joshua@froggi.es>
Co-developed-by: Melissa Wen <mwen@igalia.com>
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_color.c

@@ -72,6 +72,7 @@
  */
 
 #define MAX_DRM_LUT_VALUE 0xFFFF
+#define SDR_WHITE_LEVEL_INIT_VALUE 80
 
 /**
  * amdgpu_dm_init_color_mod - Initialize the color module.
@@ -552,6 +553,7 @@ static int amdgpu_dm_set_atomic_regamma(struct dc_stream_state *stream,
 		 */
 		out_tf->type = TF_TYPE_DISTRIBUTED_POINTS;
 		out_tf->tf = tf;
+		out_tf->sdr_ref_white_level = SDR_WHITE_LEVEL_INIT_VALUE;
 
 		ret = __set_output_tf(out_tf, regamma_lut, regamma_size, has_rom);
 	} else {