riscv: dts: microchip: add mpfs dma proxy in mpfs-disco-kit dts

commit ea83b3e639a124fbd56813443f92c41ba445e72d from
https://github.com/linux4microchip/linux.git

 linux-6.6-mchp+fpga

Add a stanza in the mpfs-disco-kit dts to support the mpfs dma proxy
driver to expose pdma channels to user space.

Signed-off-by: Valentina Fernandez <valentina.fernandezalanis@microchip.com>
Signed-off-by: harish h <harish.h@windriver.com>