iommu/s390: Fix duplicate domain attachments

Since commit fa7e9ecc5e1c ("iommu/s390: Tolerate repeat attach_dev
calls") we can end up with duplicates in the list of devices attached to
a domain. This is inefficient and confusing since only one domain can
actually be in control of the IOMMU translations for a device. Fix this
by detaching the device from the previous domain, if any, on attach.
Add a WARN_ON() in case we still have attached devices on freeing the
domain. While here remove the re-attach on failure dance as it was
determined to be unlikely to help and may confuse debug and recovery.

Fixes: fa7e9ecc5e1c ("iommu/s390: Tolerate repeat attach_dev calls")
Reviewed-by: Matthew Rosato <[email protected]>
Reviewed-by: Jason Gunthorpe <[email protected]>
Signed-off-by: Niklas Schnelle <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Joerg Roedel <[email protected]>

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