ARM: ux500: 8500: add ab8500-musb pinctrl support

Add necessary definitions to support ab8500-musb pinctrl default and
sleep states.

Signed-off-by: Patrice Chotard <patrice.chotard@stericsson.com>
Signed-off-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>