vfio/platform: remove unneeded parent_module attribute

The vfio core driver is now taking refcount on the provider drivers,
remove redundant parent_module attribute from vfio_platform_device
structure.

Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Acked-by: Eric Auger <eric.auger@redhat.com>
Link: https://lore.kernel.org/r/20210518192133.59195-3-mgurtovoy@nvidia.com


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