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>