ARM: dts: Add support for both OMAP35xx and OMAP36xx Overo/Tobi

Unfortunatly the device tree for older OMAP35xx Overo cannot be used
with newer OMAP36xx and vice-versa. To address this issue, move most of
the Tobi DTS to a common include file, and create model-specific Tobi
DTS.

Signed-off-by: Florian Vaussard <florian.vaussard@epfl.ch>
Tested-by: Kevin Hilman <khilman@linaro.org>
Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>