iommu/amd: Indicate whether DMA remap support is enabled

iommu/amd: Indicate whether DMA remap support is enabled

Bit 1 of the IVFS IVInfo field indicates that IOMMU has been used for
pre-boot DMA protection.

Export this capability to allow other places in the kernel to be able to
check for it on AMD systems.

Link: https://www.amd.com/system/files/TechDocs/48882_IOMMU.pdf
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/ce7627fa1c596878ca6515dd9d4381a45b6ee38c.1650878781.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>