[ALSA] sound/usb/usbaudio.c: fix build with CONFIG_PM=n

sound/usb/usbaudio.c: In function 'usb_audio_suspend':
sound/usb/usbaudio.c:3674: error: implicit declaration of function 'snd_pcm_sus\pend_all'

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>