[ALSA] ali5451 warning fix

sound/pci/ali5451/ali5451.c: In function 'snd_ali_prepare':
sound/pci/ali5451/ali5451.c:716: warning: 'R2' may be used uninitialized in this function

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