virtio: Replace DEFINE_PCI_DEVICE_TABLE macro use

We should prefer `struct pci_device_id` over `DEFINE_PCI_DEVICE_TABLE` to meet
kernel coding style guidelines. This issue was reported by checkpatch.

Signed-off-by: Benoit Taine <benoit.taine@lip6.fr>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>