virtualization: Add virtio-can driver as external module.

virtualization: Add virtio-can driver as external module.

This driver should conform RFC spec draft v2 [1].

This driver is based on RFC version [2].

Imported from internal OpenSynergy's revision:

  3918336a7caab95a72442c33945a193ca893d5e8

Supply build file `Kbuild` and do not supply makefile [3] since external
kernel module could be built without it. On the other hand, module
BitBake class relies on wrapper makefile presence, therefore
`MAKE_TARGETS` and `MODULES_INSTALL_TARGET` had to be set to specify
arguments per [3].

Add driver as an external module to avoid unnecessary kernel rebuild and
simplify future updates.

[1]: https://lists.oasis-open.org/archives/virtio-dev/202208/msg00159.html
[2]: https://lists.oasis-open.org/archives/virtio-dev/202208/msg00160.html
[3]: https://www.kernel.org/doc/html/v6.0/kbuild/modules.html

Change-Id: I9b654f58cc0c34983cd4103a5f7836263db79ec7
Bug-AGL: SPEC-4597
Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>