vfio/mlx5: Fix unwind flows in mlx5vf_pci_save/resume_device_data()

vfio/mlx5: Fix unwind flows in mlx5vf_pci_save/resume_device_data()

Fix unwind flows in mlx5vf_pci_save_device_data() and
mlx5vf_pci_resume_device_data() to avoid freeing the migf pointer at the
'end' label, as this will be handled by fput(migf->filp) through
mlx5vf_release_file().

To ensure mlx5vf_release_file() functions correctly, move the
initialization of migf fields (such as migf->lock) to occur before any
potential unwind flow, as these fields may be accessed within
mlx5vf_release_file().

Fixes: 9945a67ea4b3 ("vfio/mlx5: Refactor PD usage")
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20241114095318.16556-3-yishaih@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>