MIPS: xilfpga: Add DT node for AXI I2C

The xilfpga platform has an AXI I2C Bus master with a temperature
sensor connected to it.

Add the device tree node to use them.

Signed-off-by: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14594/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>