usb: gadget: u_audio: Drop superfluous ioctl PCM ops

PCM core deals the empty ioctl field now as default.
Let's kill the redundant lines.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20191210141822.18705-3-tiwai@suse.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/function/u_audio.c

@@ -314,7 +314,6 @@ static int uac_pcm_null(struct snd_pcm_substream *substream)
 static const struct snd_pcm_ops uac_pcm_ops = {
 	.open = uac_pcm_open,
 	.close = uac_pcm_null,
-	.ioctl = snd_pcm_lib_ioctl,
 	.trigger = uac_pcm_trigger,
 	.pointer = uac_pcm_pointer,
 	.prepare = uac_pcm_null,