arch-armv6m.inc: fix access rights

Signed-off-by: Ulrich Ölmann <u.oelmann@pengutronix.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 2f7ebe44)
Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>