iommu/dma: Check CONFIG_SWIOTLB more broadly

iommu/dma: Check CONFIG_SWIOTLB more broadly

Introduce a new dev_use_swiotlb function to guard swiotlb code, instead
of overloading dev_is_untrusted. This allows CONFIG_SWIOTLB to be
checked more broadly, so the swiotlb related code can be removed more
aggressively.

Signed-off-by: David Stevens <stevensd@chromium.org>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210929023300.335969-6-stevensd@google.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>