ALSA: aloop: Support return of error code for timer start and stop

This is required for additional timer implementations which could detect
errors and want to throw them.

Signed-off-by: Timo Wischer <twischer@de.adit-jv.com>
Signed-off-by: Andrew Gabbasov <andrew_gabbasov@mentor.com>
Link: https://lore.kernel.org/r/20191120174955.6410-3-andrew_gabbasov@mentor.com


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