vdpasim: allow to assign a MAC address

Add macaddr parameter to the module to set the MAC address to use

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Link: https://lore.kernel.org/r/20201029122050.776445-3-lvivier@redhat.com


Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>