vfio: correct kdoc for ops structures

vfio: correct kdoc for ops structures

Address minor omissions from kdoc for ops structures flagged by check-kdoc:

  ./scripts/kernel-doc -Werror -none include/linux/vfio.h

  include/linux/vfio.h:114: warning: Function parameter or member 'name' not described in 'vfio_device_ops'
  include/linux/vfio.h:143: warning: Cannot understand  * @migration_set_state: Optional callback to change the migration state for
   on line 143 - I thought it was a doc line
  include/linux/vfio.h:168: warning: Cannot understand  * @log_start: Optional callback to ask the device start DMA logging.
   on line 168 - I thought it was a doc line

Signed-off-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20230329120603.468031-1-horms@kernel.org
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>