ARM: dts: Add i2c-arbitrator bus for exynos5250-snow

We need to use the i2c-arbitrator to talk to any of the devices on i2c
bus 4 on exynos5250-snow so that we don't confuse the embedded
controller (EC).  Add the i2c-arbitrator to the device tree.  As we
add future devices (keyboard, sbs, tps65090) we'll add them on top of
this.

The arbitrated bus is numbered 104 simply as a convenience to make it
easier for people poking around to guess that it might have something
to do with the physical bus 4.

The addition is split between the cros5250-common and the snow device
tree file since not all cros5250-class devices use arbitration.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Olof Johansson <olof@lixom.net>