ARM: ux500: move last AB8505 set-up to DT

This moves the set-up of the HREF500 with its AB8505 ASIC to
a device tree include. Since there is not yet any device tree
for this board the DTSI is currently unused. After this delete
the board file for pins for good and migration of pins to the
device tree is complete.

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