arm64: dts: marvell: Add I2C definitions for the Armada 3700

The Armada 3700 has two i2c bus interface units, this commit adds the
definitions of the corresponding device nodes. It also enables the node
on the development board for this SoC.

Signed-off-by: Romain Perier <romain.perier@free-electrons.com>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>