virt: Add vboxguest driver for Virtual Box Guest integration

This commit adds a driver for the Virtual Box Guest PCI device used in
Virtual Box virtual machines. Enabling this driver will add support for
Virtual Box Guest integration features such as copy-and-paste, seamless
mode and OpenGL pass-through.

This driver also offers vboxguest IPC functionality which is needed
for the vboxfs driver which offers folder sharing support.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>