ARM: bcm2835: add missing #xxx-cells to I2C nodes

The I2C controller node needs #address-cells and #size-cells properties,
but these are currently missing. Add them. This allows child nodes to be
parsed correctly.

Cc: stable@vger.kernel.org
Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Olof Johansson <olof@lixom.net>