Unable to release due to git based dependencies

[rbradford]

    Updating crates.io index
error: failed to verify manifest at `/home/rbradford/src/vfio/vfio-ioctls/Cargo.toml`

Caused by:
  all dependencies must have a version requirement specified when publishing.
  dependency `iommufd-bindings` does not specify a version
  Note: The published dependency will use the version from crates.io,
  the `git` specification will be removed from the dependency declaration.

@likebreath Is it possible to get releases of these two crates so we can release vfio-ioctls

[likebreath]

@rbradford Once we land this cloud-hypervisor/iommufd#8, I should be able to publish the iommufd crates to crate.io. PTAL.

[likebreath]

@rbradford Both iommufd-bindings and iommufd-ioctls are published. Here is the PR to consume them from vfio-ioctl crate: #137.

Please let me know if it is fine to squeeze such change back to the v0.5.3.