ARM: ux500: delete custom pin control system

At the beginning of the first patch series I included the custom
ux500 pin control system to make sure I could eventually replace
it with the standard subsystem driver. So now that we've done so,
let's remove it.

Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>