ANDROID: Revert^2 "KVM: arm64: iommu: Allow to boot without IOMMU driver"

This reverts commit ede56033b2.

Reason for revert: Breaks pixel6_pkvm presubmit tests

Bug: 409494103
Change-Id: I6cf1cda14c35c748a11f0ecd31720613ffa18372
Signed-off-by: Keir Fraser <keirf@google.com>

arch/arm64/kvm/hyp/nvhe/iommu/iommu.c

@@ -215,7 +215,7 @@ int kvm_iommu_init(struct kvm_iommu_ops *ops,
 	    !ops->init ||
 	    !ops->alloc_domain ||
 	    !ops->free_domain)
-		return -ENODEV;
+		return 0;
 
 	ret = hyp_pool_init_empty(&iommu_host_pool, 64);
 	if (ret)

arch/arm64/kvm/iommu.c

@@ -42,7 +42,7 @@ int kvm_iommu_init_driver(void)
 {
 	if (!smp_load_acquire(&iommu_driver) || !iommu_driver->get_iommu_id_by_of) {
 		kvm_err("pKVM enabled without an IOMMU driver, do not run confidential workloads in virtual machines\n");
-		return -ENODEV;
+		return 0;
 	}
 
 	kvm_hyp_iommu_domains = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,