OpenRISC: Device tree

The OpenRISC architecture uses the device tree infrastructure for the
platform description.  This is currently limited to having a device tree
built into the kernel, but work is underway within the OpenRISC project
to define how this device tree blob should be passed into the kernel from
an external resource.

Patch contains a single example DTS file to go with the defconfig for
or1ksim.

Signed-off-by: Jonas Bonn <jonas@southpole.se>
Cc: devicetree-discuss@lists.ozlabs.org
Reviewed-by: Arnd Bergmann <arnd@arndb.de>