ARM: make vectors page inaccessible from userspace

If kuser helpers are not provided by the kernel, disable user access to
the vectors page.  With the kuser helpers gone, there is no reason for
this page to be visible to userspace.

Change-Id: Ia00a34e7952552634ccb03ee038cf3d0ead88459
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Git-commit: a5463cd3435475386cbbe7b06e01292ac169d36f
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[joonwoop@codeaurora.org: fixed merge conflict]
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>