devicetree will become the mandatory boot method for OMAP2+.
In order to avoid cluttering the OMAP code with #ifdef CONFIG_OF,
select USE_OF by default for every OMAP2+ systems.

Enable PROC_DEVICETREE as well.
Signed-off-by: NBenoit Cousson <b-cousson@ti.com>
Signed-off-by: NTony Lindgren <tony@atomide.com>