device_cgroup: stop using simple_strtoul()

device_cgroup: stop using simple_strtoul()

Convert the code to use kstrtou32() instead of simple_strtoul() which is
deprecated.  The real size of the variables are u32, so use kstrtou32
instead of kstrtoul

Signed-off-by: Aristeu Rozanski <aris@redhat.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: James Morris <jmorris@namei.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>