The hardware can deal with primes up to 7 and power-of-two multiples
thereof; the limitation is reflected by the possible buffer sizes.

Note that setting the voice mask will not allow more than 16 channels
even on Sound Blaster Audigy anymore, as 32 seems a bit excessive (the
code overall appears to think so, just not in this case).
Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230523200709.236059-4-oswald.buddenhagen@gmx.deSigned-off-by: Takashi Iwai <tiwai@suse.de>