MIPS: xilfpga: Update DT node and specify uart irq

Update the DT node with the UART irq

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/14593/


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