drm/amd/display: Use the correct max downscaling value for DCN3.x family

[why]
As per spec, DCN3.x can do 6:1 downscaling and DCN2.x can do 4:1. The
max downscaling limit value for DCN2.x is 250, which means it's
calculated as 1000 / 4 = 250. For DCN3.x this then gives 1000 / 6 = 167.

[how]
Set maximum downscaling limit to 167 for DCN3.x

Signed-off-by: Nikola Cornij <nikola.cornij@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Acked-by: Stylon Wang <stylon.wang@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

Author: Nikola Cornij

drivers/gpu/drm/amd/display/dc/dcn30/dcn30_resource.c

@@ -826,10 +826,11 @@ static const struct dc_plane_cap plane_cap = {
 			.fp16 = 16000
 	},
 
+	/* 6:1 downscaling ratio: 1000/6 = 166.666 */
 	.max_downscale_factor = {
-			.argb8888 = 600,
-			.nv12 = 600,
-			.fp16 = 600
+			.argb8888 = 167,
+			.nv12 = 167,
+			.fp16 = 167
 	}
 };
 

drivers/gpu/drm/amd/display/dc/dcn301/dcn301_resource.c

@@ -843,10 +843,11 @@ static const struct dc_plane_cap plane_cap = {
 			.fp16 = 16000
 	},
 
+	/* 6:1 downscaling ratio: 1000/6 = 166.666 */
 	.max_downscale_factor = {
-			.argb8888 = 600,
-			.nv12 = 600,
-			.fp16 = 600
+			.argb8888 = 167,
+			.nv12 = 167,
+			.fp16 = 167 
 	},
 	64,
 	64

drivers/gpu/drm/amd/display/dc/dcn302/dcn302_resource.c

@@ -284,10 +284,11 @@ static const struct dc_plane_cap plane_cap = {
 				.nv12 = 16000,
 				.fp16 = 16000
 		},
+		/* 6:1 downscaling ratio: 1000/6 = 166.666 */
 		.max_downscale_factor = {
-				.argb8888 = 600,
-				.nv12 = 600,
-				.fp16 = 600
+				.argb8888 = 167,
+				.nv12 = 167,
+				.fp16 = 167
 		},
 		16,
 		16