Create GPIO device for existing DaVinci boards.

While at it, group related header files together.
Signed-off-by: NPhilip Avinash <avinashphilip@ti.com>
Signed-off-by: NLad, Prabhakar <prabhakar.csengg@gmail.com>
Acked-by: NLinus Walleij <linus.walleij@linaro.org>
[nsekhar@ti.com: remove soc bits from this patch and
		 simplify commit message]
Signed-off-by: NSekhar Nori <nsekhar@ti.com>