drm/amd/display: Add condition for dp_set_dsc_config call

Not every ASIC implements dp_set_dsc_config. Add condition to prevent
calls to unimplemented function.
Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Ilya Bakoulin <ilya.bakoulin@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/link/link_dpms.c

@@ -838,6 +838,7 @@ void link_set_dsc_on_stream(struct pipe_ctx *pipe_ctx, bool enable)
 		if (dc_is_dp_signal(stream->signal) && !dp_is_128b_132b_signal(pipe_ctx)) {
 			DC_LOG_DSC("Setting stream encoder DSC config for engine %d:", (int)pipe_ctx->stream_res.stream_enc->id);
 			dsc_optc_config_log(dsc, &dsc_optc_cfg);
+			if (pipe_ctx->stream_res.stream_enc->funcs->dp_set_dsc_config)
 				pipe_ctx->stream_res.stream_enc->funcs->dp_set_dsc_config(pipe_ctx->stream_res.stream_enc,
 										optc_dsc_mode,
 										dsc_optc_cfg.bytes_per_pixel,
@@ -868,6 +869,7 @@ void link_set_dsc_on_stream(struct pipe_ctx *pipe_ctx, bool enable)
 										NULL,
 										true);
 			else {
+				if (pipe_ctx->stream_res.stream_enc->funcs->dp_set_dsc_config)
 					pipe_ctx->stream_res.stream_enc->funcs->dp_set_dsc_config(
 							pipe_ctx->stream_res.stream_enc,
 							OPTC_DSC_DISABLED, 0, 0);