ARM: dts: Add aliases for i2c controller for exynos4

This is similar to a recent commit for exynos5250 titled:
  ARM: EXYNOS: Add aliases for i2c controller

Adding aliases will be useful to prevent warnings in a future
change. See:
  i2c: s3c2410: Get the i2c bus number from alias id

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