ARM: ux500: move MSP pin control to the device tree

This moves the static, device-tied pin control configuration
out of the board file board-mop500-pins.c and into the device
tree. Add nodes for MSP0 and MSP2 on the HREF and Snowball
so we can reference the pins properly.

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