ARM: plat-iop: pass physical base for GPIO

This alters the IOP platforms to pass a physical base for their
GPIO blocks and alters the driver to remap it when probing
instead of relying on the virtual addresses to be used.

Cc: Lennert Buytenhek <kernel@wantstofly.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Mikael Pettersson <mikpe@it.uu.se>
Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>