usb: gadget: u_audio: Remove superfluous snd_dma_continuous_data()

The recent change (commit 08422d2c: "ALSA: memalloc: Allow NULL
device for SNDRV_DMA_TYPE_CONTINUOUS type") made the PCM preallocation
helper accepting NULL as the device pointer for the default usage.
Drop the snd_dma_continuous_data() usage that became superfluous from
the callers.
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20191108164214.611-1-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

drivers/usb/gadget/function/u_audio.c

@@ -585,7 +585,7 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
 	sprintf(card->longname, "%s %i", card_name, card->dev->id);
 
 	snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_CONTINUOUS,
-		snd_dma_continuous_data(GFP_KERNEL), 0, BUFF_SIZE_MAX);
+					      NULL, 0, BUFF_SIZE_MAX);
 
 	err = snd_card_register(card);