ALSA: pcm: Use __ffs() instead of ffs() in snd_mask_min()

The difference between __ffs and ffs is that ffs will return a one based
index whereas __ffs will return a zero based index. Furthermore ffs will
check if the passed value is zero and return zero in that case, whereas
__ffs behavior is undefined if the passed parameter is 0.

Since we already check if the mask is 0 before calling ffs and also subtract
1 from the result __ffs is the better choice.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/sound/pcm_params.h

@@ -92,7 +92,7 @@ static inline unsigned int snd_mask_min(const struct snd_mask *mask)
 	int i;
 	for (i = 0; i < SNDRV_MASK_SIZE; i++) {
 		if (mask->bits[i])
-			return ffs(mask->bits[i]) - 1 + (i << 5);
+			return __ffs(mask->bits[i]) + (i << 5);
 	}
 	return 0;
 }