Add BSP for Polarfire based Beagle

There is a new RISC-V based Beagle based on the Polarfire SOC. This project is to create a BSP for that.

The following is a list of peripherals that have been identified based on information from https://www.microchip.com/en-us/products/fpgas-and-plds/system-on-chip-fpgas/polarfire-soc-fpgas

Another dev kit could be https://www.microchip.com/en-us/development-tool/mpfs-disco-kit

This ticket is related to the BeagleBoard 2022 GSoC effort: https://elinux.org/BeagleBoard/GSoC/Ideas-2022#RTEMS_on_RISC-V

As of 2022/3/1, at least these BSP components are supported:

• CPU Cores (both E51 and U54)
• Interrupt controller (PLIC)
• Timer (CLINT)
• UART (mmuart, 16550-compatible or close enough)

Unsupported:

• Ethernet (mss-gem, not in libbsd or upstream FreeBSD, lwIP support unknown)
• U54 MMU (bare and Sv39 modes)

There is Linux support under development for this. We need to pursue asking for dual-licensing at least the network driver as NXP did for qoriq.

All other peripherals have not been checked for existing support.

Mentors: Hesham, Kinsey, Joel, Chris, someone from Beagle community Skills: C