iommu: Checking for NULL instead of IS_ERR
iommu: Checking for NULL instead of IS_ERR

The iommu_group_alloc() and iommu_group_get_for_dev()
functions return error pointers, they never return NULL.

Signed-off-by: Dan Carpenter <ff341aa343d564f9e53e9dcb6996be8c04859a66@oracle.com>
Signed-off-by: Joerg Roedel <61aff96566804ea1da8a65de5bcc892ce07caceb@suse.de>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs