IOMMU/x86: don't bypass softirq processing in arch_iommu_hwdom_init()

IOMMU/x86: don't bypass softirq processing in arch_iommu_hwdom_init()

Even when a page doesn't need mapping, we should check whether softirq
processing should be invoked. Otherwise with sufficiently much RAM
chances of a to-be-mapped page actually occurring with the loop counter
having the "right" value may become diminishingly small.

Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Tested-by: Andrew Cooper <andrew.cooper3@citrix.com>