AMD/IOMMU: disable previously enabled IOMMUs upon init failure

AMD/IOMMU: disable previously enabled IOMMUs upon init failure

If any IOMMUs were successfully initialized before encountering failure,
the successfully enabled ones should be disabled again before cleaning
up their resources.

Move disable_iommu() next to enable_iommu() to avoid a forward
declaration, and take the opportunity to remove stray blank lines ahead
of both functions' final closing braces.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Brian Woods <brian.woods@amd.com>