ALSA: emu10k1: make E-MU mixer control creation more data-driven

The more card models are handled separately, the more code duplication
this saves.

add_emu1010_source_mixers() is factored out the save duplication in a
later commit.

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230516093612.3536508-8-oswald.buddenhagen@gmx.de


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