vfio-iommufd: No need to record iommufd_ctx in vfio_device

vfio-iommufd: No need to record iommufd_ctx in vfio_device

iommufd_ctx is stored in vfio_device for emulated devices per bind_iommufd.
However, as iommufd_access is created in bind, no more need to stored it
since iommufd_access implicitly stores it.

Link: https://lore.kernel.org/r/20230327093351.44505-4-yi.l.liu@intel.com
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Terrence Xu <terrence.xu@intel.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>