audio: mux: Fix use of incorrect macro

comp_buffer_get_sink_component(b) inside a for_each_producer loop
returns mux itself, making the pipeline comparison always false and
audio_stream_set_overrun() unreachable.

Issue found using semgrep with custom rules.

Signed-off-by: Tomasz Leman <tomasz.m.leman@intel.com>

Author: tmleman

src/audio/mux/mux.c

@@ -292,7 +292,7 @@ static int demux_trigger(struct processing_module *mod, int cmd)
 		struct comp_buffer *b;
 
 		comp_dev_for_each_producer(mod->dev, b) {
-			if (comp_buffer_get_sink_component(b)->pipeline != mod->dev->pipeline)
+			if (comp_buffer_get_source_component(b)->pipeline != mod->dev->pipeline)
 				audio_stream_set_overrun(&b->stream, true);
 		}
 	}