ARM: dts: Add basic support for zoom3

I've tested serial, MMC, smsc911x and wl12xx on zoom3. As my
omap is an early ES revision, I have not been able to test
off-idle on this one. But anyways, I'd say we have enough
device tree support for the zoom to be able to drop the
board-zoom files. Patches are welcome to add further features
to this .dts file.

Signed-off-by: Tony Lindgren <tony@atomide.com>