ALSA: uapi: Drop asound.h inclusion from asoc.h

The asound.h isn't always available while asoc.h itself is distributed
in alsa-lib package.  So we need to avoid the unnecessary inclusion of
asound.h from there.

Link: https://lore.kernel.org/r/20191220153415.2740-6-tiwai@suse.de


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