xen: arm: weaken SMP barriers to inner shareable.

xen: arm: weaken SMP barriers to inner shareable.

Since all processors are in the inner-shareable domain and we map everything
that way this is sufficient.

The non-SMP barriers remain full system. Although in principle they could
become outer shareable barriers for some hardware this would require us to
know which class a given device is. Given the small number of device drivers
in Xen itself its probably not worth worrying over, although maybe someone
will benchmark at some point.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Tim Deegan <tim@xen.org>