vfio/pci: Remove unused struct 'vfio_pci_mmap_vma'

'vfio_pci_mmap_vma' has been unused since
commit aac6db75 ("vfio/pci: Use unmap_mapping_range()")

Remove it.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20240727160307.1000476-1-linux@treblig.org


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