drm/amd/display: fix issue where 252-255 values are clipped

[ Upstream commit 1cbcfc975164f397b449efb17f59d81a703090db ]

[Why]
When endpoint is at the boundary of a region, such as at 2^0=1
we find that the last segment has a sharp slope and some points
are clipped at the top.

[How]
If end point is 1, which is exactly at the 2^0 region boundary, we
need to program an additional region beyond this point.
Signed-off-by: NAnthony Koo <Anthony.Koo@amd.com>
Reviewed-by: NAric Cyr <Aric.Cyr@amd.com>
Acked-by: NLeo Li <sunpeng.li@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_cm_common.c

@@ -292,9 +292,10 @@ bool cm_helper_translate_curve_to_hw_format(
 		seg_distr[7] = 4;
 		seg_distr[8] = 4;
 		seg_distr[9] = 4;
+		seg_distr[10] = 1;
 
 		region_start = -10;
-		region_end = 0;
+		region_end = 1;
 	}
 
 	for (i = region_end - region_start; i < MAX_REGIONS_NUMBER ; i++)