ALSA: synth: Select snd-emux-synth explicitly

Instead of the non-standard way to enable the build of snd-emux-synth
module inside Makefile, rewrite Kconfig to select the item explicitly
from each driver (sbawe and emu10k1).  This is the standard way.

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