avdevice/pulse_audio_common: add av_warn_unused_result

This does not trigger any warnings, but adds robustness.
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>

libavdevice/pulse_audio_common.h

@@ -28,8 +28,10 @@
 
 pa_sample_format_t ff_codec_id_to_pulse_format(enum AVCodecID codec_id);
 
+av_warn_unused_result
 int ff_pulse_audio_get_devices(AVDeviceInfoList *devices, const char *server, int output);
 
+av_warn_unused_result
 int ff_pulse_audio_connect_context(pa_mainloop **pa_ml, pa_context **pa_ctx,
                                    const char *server, const char *description);