drm/amd/display: Keep current gain when ABM disable immediately

[Why]
When system enters s3/s0i3, backlight PWM would set user level.

[How]
ABM disable function add keep current gain to avoid it.
Signed-off-by: Brandon Syu <Brandon.Syu@amd.com>
Reviewed-by: Josip Pavic <Josip.Pavic@amd.com>
Acked-by: Eryk Brol <eryk.brol@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dc_stream.h

@@ -233,7 +233,7 @@ struct dc_stream_state {
 	union stream_update_flags update_flags;
 };
 
-#define ABM_LEVEL_IMMEDIATE_DISABLE 0xFFFFFFFF
+#define ABM_LEVEL_IMMEDIATE_DISABLE 255
 
 struct dc_stream_update {
 	struct dc_stream_state *stream;