xenops_interface: add vgpu-to-pci map to VM.migrate
xenops_interface: add vgpu-to-pci map to VM.migrate

This is similar to the existing VBD and VIF maps.

Signed-off-by: Rob Hoes <8783b3376fb07d39edffc8d7da68a6de3874a7e6@citrix.com>

xapi-project/message-switch,xapi-project/message-switch,xapi-project/message-switch