mei: virtio: virtualization frontend driver

mei: virtio: virtualization frontend driver

This frontend driver implements MEI hw interface based on virtio
framework to let MEI driver work without changes under virtualization.
It requires a backend service in the ACRN device-model on the service
OS side to make it work. The backend service will emulate mei routing
and assign vtags for each mei vritio device.

The backend service is available in ACRN device-model at github.
For more information, please refer to https://projectacrn.org

The ACRN virtio sub device id for MEI is is 0x8602.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Wang Yu <yu1.wang@intel.com>
Signed-off-by: Liu Shuo <shuo.a.liu@intel.com>
Link: https://lore.kernel.org/r/20200818115147.2567012-14-tomas.winkler@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>