drm/amd/display: Update 128b/132b downspread factor to 0.3%

[Why]
Updating downspread factor to 0.3% to add additional margin to account
for potential link rate deviations (up to 300ppm as per the DP spec).
Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Acked-by: Alan Liu <haoping.liu@amd.com>
Signed-off-by: George Shen <george.shen@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/include/link_service_types.h

@@ -53,7 +53,7 @@ enum {
 	BITS_PER_DP_BYTE = 10,
 	DATA_EFFICIENCY_8b_10b_x10000 = 8000, /* 80% data efficiency */
 	DATA_EFFICIENCY_8b_10b_FEC_EFFICIENCY_x100 = 97, /* 97% data efficiency when FEC is enabled */
-	DATA_EFFICIENCY_128b_132b_x10000 = 9646, /* 96.71% data efficiency x 99.75% downspread factor */
+	DATA_EFFICIENCY_128b_132b_x10000 = 9641, /* 96.71% data efficiency x 99.7% downspread factor */
 };
 
 enum lttpr_mode {