ARM: ux500: move AB8500 GPIOs to device tree

Move the AB8500 muxing and biasing settings over from the board
file to the device tree, include it in the reference designs using
the AB8500: HREF prior to v60, v60plus and Snowball. Set up these
GPIO lines using hogs, just like in the board file.

Cc: Patrice Chotard <patrice.chotard@st.com>
Cc: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>