vfio/ccw: Refactor vfio_ccw_mdev_reset

Use both the FSM Close and Open events when resetting an mdev,
rather than making a separate call to cio_enable_subchannel().

Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Link: https://lore.kernel.org/r/20220707135737.720765-11-farman@linux.ibm.com


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