Add devicetree source files as of Linux-3.15-rc2 ...

This adds the Linux dts files to barebox. The dts files are
generated from Ian Campbells device-tree-rebasing.git:

git://xenbits.xen.org/people/ianc/device-tree-rebasing.git

The dts are found in dts/ in the barebox repository and
will be updated from upstream regularly, probably for each upstream
-rc.

To keep the synchronization with upstream easy no changes to
the original files are allowed under dts/. Instead changes to
upstream dts files will be done using overlays in arch/$ARCH/dts/.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>