ALSA: emu10k1: remove unused snd_emu10k1_voice.emu field

It was written, but never read from. Its value is available via the epcm
field.

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230421141006.1005452-5-oswald.buddenhagen@gmx.de


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