riscv: dts: microchip: add an initial devicetree for the BeagleV Fire

riscv: dts: microchip: add an initial devicetree for the BeagleV Fire

Add an initial devicetree for the BeagleV Fire. This devicetree differs
from that in the BeagleBoard BSP as it has a different memory
configuration, however it will boot on the same FPGA images. PCI is
disabled for now, as the Linux PCI driver (and the binding) assume
which root port instance is in use. This will need to be fixed before
PCI can be enabled.

Link: https://www.beagleboard.org/boards/beaglev-fire
Co-developed-by: Jamie Gibbons <jamie.gibbons@microchip.com>
Signed-off-by: Jamie Gibbons <jamie.gibbons@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>