ANDROID: KVM: arm64: iommu: Avoid ref count leak when __pkvm_host_use_dma fails

In kvm_iommu_map_pages, release the reference to the domain if we return
early because __pkvm_host_use_dma failed.

Bug: 401132481
Fixes: a737b7d0e721 ("ANDROID: KVM: arm64: iommu: Reduce the logic in generic code")
Change-Id: Ib792425a726513f5a6b8198aa3d0208aa43b0502
Signed-off-by: Daniel Mentz <danielmentz@google.com>
Signed-off-by: Mostafa Saleh <smostafa@google.com>

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

@@ -484,7 +484,7 @@ size_t kvm_iommu_map_pages(pkvm_handle_t domain_id,
 
 	ret = __pkvm_use_dma(paddr, size, __get_vcpu());
 	if (ret)
-		return 0;
+		goto out_put_domain;
 
 	kvm_iommu_ops->map_pages(domain, iova, paddr, pgsize, pgcount, prot, &total_mapped);
 
@@ -497,6 +497,7 @@ size_t kvm_iommu_map_pages(pkvm_handle_t domain_id,
 	if (pgcount)
 		__pkvm_unuse_dma(paddr + total_mapped, pgcount * pgsize, __get_vcpu());
 
+out_put_domain:
 	domain_put(domain);
 	return total_mapped;
 }