vfio/pci: Simplify the is_intx/msi/msix/etc defines

Only three of these are actually used, simplify to three inline functions,
and open code the if statement in vfio_pci_config.c.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Link: https://lore.kernel.org/r/3-v2-1bd95d72f298+e0e-vfio_pci_priv_jgg@nvidia.com


Signed-off-by: Alex Williamson <alex.williamson@redhat.com>