ALSA: timer: Simplify error path in snd_timer_open()

[ Upstream commit 41672c0c ]

Just a minor refactoring to use the standard goto for error paths in
snd_timer_open() instead of open code.  The first mutex_lock() is
moved to the beginning of the function to make the code clearer.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>