meta-agl-core: systemd: Disable `BitRate` setting for `can*` network for VIRTIO.

meta-agl-core: systemd: Disable `BitRate` setting for `can*` network for VIRTIO.

VIRTIO CAN [1] does not support bitrate configuration, it assumes
bitrate configuration is done on backend.

Fixes systemd-networkd failure:

    can0: Failed to set CAN interface configurations: Operation not supported

File `canbus-virtio-can.network` is copied from `canbus-can.network`
with `BitRate=` setting removed.

v2: rework patchset to use own systemd-conf-canbus package to
    avoid changes in main systemd package.

[1]: https://lists.oasis-open.org/archives/virtio-dev/202208/msg00159.html

Bug-AGL: SPEC-4597

Change-Id: Idb132203501bb99103e76098eea3bb6394b645da
Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/28104
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>