ACPI/IORT: Use device_iommu_mapped()

Replace the iommu-check with a proper and readable function
call.

Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: Joerg Roedel <jroedel@suse.de>