- Add details of pins usage.
  - List all FPGA pin assignments to headers P8 and P9.

  - Marked pins not available in the MPFS025-FCVG484 package.
  - Identified available pins not currently used in the design.
  - Identified pins used in the design that need to be properly
    document (marked as GPIO?).

Cleared up README from information regarding the base reference design
used as a starting point.

Use PolarFire SoC Icicle Kit Reference Design as starting point:
  https://github.com/polarfire-soc/icicle-kit-reference-design
  hash: 4c95670cc11bd428d6bec592058f7e86b7b4fa94