ARM: nomadik: push accelerometer down to boards

The two Nomadik variants have the accelerometer mounted on
different I2C lines. Push the definition down to the top-level
board DTS files to get things right.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>