aplay: fix VU meter for S24_LE etc formats

aplay: fix VU meter for S24_LE etc formats

When recording or playing back audio in a format where the number of
significant bits is less than the physical width (e.g. S24_LE), the VU
meter code needs to consider the number of significant bits in the samples
rather than the physical sample width (e.g. 24 vs 32 bits). Otherwise the
resulting VU meter display will be far too low and it will just indicate
0% all the time.

Tested with a device supporting the S24_LE format.

Signed-off-by: Ricard Wanderlof <ricardw@axis.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>