drm/amd/display: Limit user regamma to a valid value

[Why]
For HDR mode, we get total 512 tf_point and after switching to SDR mode
we actually get 400 tf_point and the rest of points(401~512) still use
dirty value from HDR mode. We should limit the rest of the points to max
value.

[How]
Limit the value when coordinates_x.x > 1, just like what we do in
translate_from_linear_space for other re-gamma build paths.
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Pavle Kotarac <Pavle.Kotarac@amd.com>
Signed-off-by: Yao Wang1 <Yao.Wang1@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/modules/color/color_gamma.c

@@ -1600,6 +1600,7 @@ static void interpolate_user_regamma(uint32_t hw_points_num,
 	struct fixed31_32 lut2;
 	struct fixed31_32 delta_lut;
 	struct fixed31_32 delta_index;
+	const struct fixed31_32 one = dc_fixpt_from_int(1);
 
 	i = 0;
 	/* fixed_pt library has problems handling too small values */
@@ -1628,6 +1629,9 @@ static void interpolate_user_regamma(uint32_t hw_points_num,
 			} else
 				hw_x = coordinates_x[i].x;
 
+			if (dc_fixpt_le(one, hw_x))
+				hw_x = one;
+
 			norm_x = dc_fixpt_mul(norm_factor, hw_x);
 			index = dc_fixpt_floor(norm_x);
 			if (index < 0 || index > 255)