iommu: Initialize domain->handler in iommu_domain_alloc()

Since it is not guaranteed that an iommu driver initializes in its
domain_init() function, it must be initialized with NULL to prevent
calling a function in an arbitrary location when iommu fault occurred.
Signed-off-by: KyongHo Cho <pullip.cho@samsung.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

drivers/iommu/iommu.c

@@ -90,7 +90,7 @@ struct iommu_domain *iommu_domain_alloc(struct bus_type *bus)
 	if (bus == NULL || bus->iommu_ops == NULL)
 		return NULL;
 
-	domain = kmalloc(sizeof(*domain), GFP_KERNEL);
+	domain = kzalloc(sizeof(*domain), GFP_KERNEL);
 	if (!domain)
 		return NULL;