alsa-state: install init script only when 'sysvinit' is in DISTRO_FEATURES

alsa-state: install init script only when 'sysvinit' is in DISTRO_FEATURES

The /etc/init.d/alsa-state is totally useless for a systemd image.
Its functionality has been replaced by alsa-state.service files.

So if 'sysvinit' is not in DISTRO_FEATURES, installing this script doesn't
make any sense.

[YOCTO #4420]

(From OE-Core rev: 39759640c8abe51c8ded4c1ca6853b523a81c2f5)

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>