drm/amd/display: 3-plane MPO enablement for DCN321

Enable 3-planes MPO for DCN321 by reporting max_slave_planes in DC caps
for each ASIC.
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn321/dcn321_resource.c

@@ -1727,9 +1727,9 @@ static bool dcn321_resource_construct(
 	dc->caps.subvp_pstate_allow_width_us = 20;
 	dc->caps.subvp_vertical_int_margin_us = 30;
 	dc->caps.subvp_drr_vblank_start_margin_us = 100; // 100us margin
-	dc->caps.max_slave_planes = 1;
-	dc->caps.max_slave_yuv_planes = 1;
-	dc->caps.max_slave_rgb_planes = 1;
+	dc->caps.max_slave_planes = 2;
+	dc->caps.max_slave_yuv_planes = 2;
+	dc->caps.max_slave_rgb_planes = 2;
 	dc->caps.post_blend_color_processing = true;
 	dc->caps.force_dp_tps4_for_cp2520 = true;
 	dc->caps.dp_hpo = true;