ARM: mx25: move registration of gpios to plat-mxc/gpio.c

ARM: mx25: move registration of gpios to plat-mxc/gpio.c

To use common macros to define the gpio ports for imx{1,21,25,27} the
existing ones had to made more general and a few more base address defines
were necessary.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>