iommu/amd: use full 64-bit value in build_completion_wait()

We started using a 64 bit completion value.  Unfortunately, we only
stored the low 32-bits, so a very large completion value would never
be matched in iommu_completion_wait().

Fixes: c69d89af ("iommu/amd: Use 4K page for completion wait write-back semaphore")
Signed-off-by: John Sperbeck <jsperbeck@google.com>
Link: https://lore.kernel.org/r/20220801192229.3358786-1-jsperbeck@google.com


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