arc: use patched .dts from sources

arc: use patched .dts from sources

Instead of using off-the-tree .dts files for ARC boards we're
switching to use in-tree ones. And for that to work properly
we apply upstream patch that adds currently missing "model"
property.

Upstream patch and discussion could be found here:
http://lists.infradead.org/pipermail/linux-snps-arc/2016-August/001394.html

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Jonas Gorski <jonas.gorski@gmail.com>
Cc: John Crispin <john@phrozen.org>