ALSA: emu10k1: skip pointless cache setup for extra voices

Given that the data is going to be ignored anyway, and that the cache
does not influence interrupt timing (which is the purpose of the extra
voices), it's pointless to pre-fill the cache.

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230517174256.3657060-4-oswald.buddenhagen@gmx.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>