ALSA: usb-audio: Remove the repeated declaration

Function 'snd_usb_endpoint_suspend' is declared twice, so remove the
repeated declaration.

Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Link: https://lore.kernel.org/r/1622278926-63857-1-git-send-email-zhangshaokun@hisilicon.com


Signed-off-by: Takashi Iwai <tiwai@suse.de>