iommu/amd: Remove dma_mask check from check_device()

The check was only needed for the DMA-API implementation in the AMD
IOMMU driver, which no longer exists.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Link: https://lore.kernel.org/r/20200429133712.31431-6-joro@8bytes.org


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