gpio: davinci: Move driver local definitions to driver

These defines, structs and inline functions are used only internally by
the driver, they do not belong in platform_data. Move them.

Signed-off-by: Andrew F. Davis <afd@ti.com>
Tested-by: Keerthy <j-keerthy@ti.com>
Acked-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>