make W=1 warning:

sound/virtio/virtio_ctl_msg.c:70: warning: expecting prototype for
virtsnd_ctl_msg_request(). Prototype was for
virtsnd_ctl_msg_response() instead
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20210426213902.234711-1-pierre-louis.bossart@linux.intel.comSigned-off-by: Takashi Iwai <tiwai@suse.de>