alsactl: Remove standard output definition in systemd unit

alsactl: Remove standard output definition in systemd unit

`/lib/systemd/system/alsa-restore.service` specifies
`StandardOutput=syslog`. This overrides the `DefaultStandardOutput`
setting from `/etc/systemd/system.conf`, which the system administrator
can use to specify how output gets logged. In particular, the sysadmin
may want output to go to the journal, or to syslog, or nowhere at all [1].

This patch removes the definition entirely, so the units can use the
system default.

Upstream the patch from the Debian package [2].

[1] https://bugs.debian.org/741123
    "systemd services should not use StandardOutput=syslog; should rely
     on DefaultStandardOutput"
[2] https://sources.debian.net/src/alsa-utils/1.1.2-1/debian/patches/systemd_standardoutput.patch/

Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
CC: Jordi Mallach <jordi@debian.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>