drm/amd/display: Secondary display goes blank on Non DCN31

[Why]
Due to integration issues with branch merging,
a regression happened that prevented secondary
displays from lighting up or enabling certain features

[How]
Separated the new logic to be for DCN31 only and retained
pre DCN31 logic for all other ASICs
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Ahmad Othman <Ahmad.Othman@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/core/dc_link.c

@@ -3997,7 +3997,8 @@ static void update_psp_stream_config(struct pipe_ctx *pipe_ctx, bool dpms_off)
 			config.phy_idx = link_enc->transmitter - TRANSMITTER_UNIPHY_A;
 
 			// Add flag to guard new A0 DIG mapping
-			if (pipe_ctx->stream->ctx->dc->enable_c20_dtm_b0 == true) {
+			if (pipe_ctx->stream->ctx->dc->enable_c20_dtm_b0 == true &&
+					pipe_ctx->stream->link->dc->ctx->dce_version == DCN_VERSION_3_1) {
 				config.dig_be = link_enc->preferred_engine;
 				config.dio_output_type = pipe_ctx->stream->link->ep_type;
 				config.dio_output_idx = link_enc->transmitter - TRANSMITTER_UNIPHY_A;