ALSA: virtio: use module_virtio_driver() to simplify the code

module_virtio_driver() makes the code simpler by eliminating
boilerplate code.

Signed-off-by: Chen Huang <chenhuang5@huawei.com>
Reviewed-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
Link: https://lore.kernel.org/r/20210408125429.1158703-1-chenhuang5@huawei.com


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