pinctrl/abx500: add AB8505 sub-driver

Add AB8505 sub driver to the ABx5x family.

As the pin controller (also the ABx500 controllers) is an
inherent part of the SoC and will prevent boot if not
available, select this from the Ux500 SoC Kconfig.

Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Patrice Chotard <patrice.chotard@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>