ARM: davinci: support gpio platform device

DaVinci GPIO driver now uses platform device model.
Add a GPIO platform register API to convert the
traditional DaVinci  SoCs to use the new model.

While at it, also group related include files together
wherever that was not the case.

Signed-off-by: Philip Avinash <avinashphilip@ti.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
[nsekhar@ti.com: move function declaration to local header,
		 simplify commit message, merge SoC specific
		 portions from other patches into this patch]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>