Add minimal device tree support for n8x0 boards so we
can make omap2 device tree only. Note that we still need
to initialize various platform data quirks to keep
things working until n8x0 drivers support device tree.

Here's a rough todo list for the people using n8x0:

1. Update menelaus for device tree and set up
   regulators at least for the MMC driver

2. Remove the MMC regulator platform data callback
   by using the Menlaus regulators directly in the
   driver passed from the .dts file

3. Update GPMC connected devices for onenand and
   tusb6010 for device tree

We're planning to remove all legacy platform data
for mach-omap2 over next few merge cycles, so if
people are still using n8x0, please fix the issues
above.

Cc: devicetree@vger.kernel.org
Cc: "Benoît Cousson" <bcousson@baylibre.com>
Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Tony Lindgren <tony@atomide.com>