iommu: Make iommu_release_device() static

This is not called outside the core code, and indeed cannot be called
correctly outside the bus notifier. Make it static.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/0-v1-c3da18124d2d+56-rm_iommu_release_jgg@nvidia.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>