vfio: no need to pass kvm pointer during device open

Nothing uses this value during vfio_device_open anymore so it's safe
to remove it.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Tested-by: Tony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Yi Liu <yi.l.liu@intel.com>
Link: https://lore.kernel.org/r/20230203215027.151988-3-mjrosato@linux.ibm.com


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