iommu: Fix return code in iommu_group_alloc_default_domain()

This function returns NULL on errors, not ERR_PTR.

Fixes: 1c68cbc ("iommu: Add IOMMU_DOMAIN_PLATFORM")
Reported-by: Dan Carpenter <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jason Gunthorpe <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Joerg Roedel <[email protected]>

Author: jgunthorpe

drivers/iommu/iommu.c

@@ -1787,7 +1787,7 @@ iommu_group_alloc_default_domain(struct iommu_group *group, int req_type)
 	 */
 	if (ops->default_domain) {
 		if (req_type)
-			return ERR_PTR(-EINVAL);
+			return NULL;
 		return ops->default_domain;
 	}