virtio: Backport virtio sound driver.

virtio: Backport virtio sound driver.

Added patch series is the latest implementation [1] of virtio sound
device [2] driver. It was accepted [3] by sound maintainer for the next
kernel version.

virtio-snd.cfg snippet has been generated using menuconfig/diffconfig
tasks by selecting SND_VIRTIO, other configs have been selected
automatically.

[1]: https://lore.kernel.org/alsa-devel/20210302164709.3142702-1-anton.yakovlev@opensynergy.com/
[2]: https://github.com/oasis-tcs/virtio-spec/blob/master/virtio-sound.tex
[3]: https://lore.kernel.org/alsa-devel/s5hsg575q5z.wl-tiwai@suse.de/

Bug-AGL: SPEC-3894
Change-Id: Ide484b4a70e5d2aef0726f701f87d783e128c4d3
Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/26291
Tested-by: Jenkins Job builder account
ci-image-build: Jenkins Job builder account
ci-image-boot-test: Jenkins Job builder account
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>