PCI/P2PDMA: Allow IOMMU for host bridge whitelist

Now that we map the requests correctly we can remove the iommu_present()
restriction.

Link: https://lore.kernel.org/r/20190730163545.4915-14-logang@deltatee.com
Link: https://lore.kernel.org/r/20190812173048.9186-14-logang@deltatee.comSigned-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

drivers/pci/p2pdma.c

@@ -18,7 +18,6 @@
 #include <linux/percpu-refcount.h>
 #include <linux/random.h>
 #include <linux/seq_buf.h>
-#include <linux/iommu.h>
 #include <linux/xarray.h>
 
 enum pci_p2pdma_map_type {
@@ -328,9 +327,6 @@ static bool host_bridge_whitelist(struct pci_dev *a, struct pci_dev *b)
 	struct pci_host_bridge *host_a = pci_find_host_bridge(a->bus);
 	struct pci_host_bridge *host_b = pci_find_host_bridge(b->bus);
 
-	if (iommu_present(a->dev.bus) || iommu_present(b->dev.bus))
-		return false;
-
 	if (host_a == host_b)
 		return __host_bridge_whitelist(host_a, true);