iommu/core: Convert iommu_found to iommu_present

With per-bus iommu_ops the iommu_found function needs to
work on a bus_type too. This patch adds a bus_type parameter
to that function and converts all call-places.
The function is also renamed to iommu_present because the
function now checks if an iommu is present for a given bus
and does not check for a global iommu anymore.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
index 20115b1..d149940 100644
--- a/virt/kvm/iommu.c
+++ b/virt/kvm/iommu.c
@@ -228,7 +228,7 @@
 {
 	int r;
 
-	if (!iommu_found()) {
+	if (!iommu_present(&pci_bus_type)) {
 		printk(KERN_ERR "%s: iommu not found\n", __func__);
 		return -ENODEV;
 	}