pinctrl: imx1 core driver

Core driver for register formats of imx1/imx21/imx27 processors.

The pins of those processors are grouped into ports. Each port has 32
pins. The pins mux configuration is controlled by registers with 1 or 2
bit per pin, depending on the specific control register.

Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>