ARM: ux500: move I2C 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. Define possible states also for I2C4 even if it's not
used by any board file at this time.

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