intel_ips: potential null dereference

There is a potential NULL dereference of "limits."  We can just return
NULL earlier to avoid it.  The caller already handles NULL returns.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Matthew Garrett <mjg@redhat.com>