igd is related to the vfio_pci pci_driver implementation, move it out of
vfio_pci_core.c.

This is preparation for splitting vfio_pci.ko into 2 drivers.
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Link: https://lore.kernel.org/r/20210826103912.128972-8-yishaih@nvidia.comSigned-off-by: Alex Williamson <alex.williamson@redhat.com>