ARM: versatile: move GPIO2 and GPIO3 to core

Move GPIO2 and GPIO3 to be registered from the core as this is
certainly available on Versatile AB as well, not just the PB.
GPIO2 is used for reading board status and GPIO3 is unused,
but it does not hurt to register it anyway.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>