Clean-up and harden the RISC-V64 GNU port

[fdesbiens]

Objective

Improve code quality and maintainability of the existing RISC-V64/GNU ThreadX port.

Deliverables

• Improve and expand code comments to describe design intent, context switch logic, and assembly behavior.
• Standardize function names, labels, and macros to conform with RISC-V naming conventions and ThreadX coding standards.
• Eliminate hardcoded constants (e.g., stack offsets, register counts) by replacing them with macros, enums, or configuration flags.
• Create and document reusable flags/definitions for ISA features, register widths, ABI handling, and toolchain specifics.
• Ensure the port is fully documented and baseline compliant with RISC-V ISA (privileged architecture) expectations.

Tags

Cleanup, Low Complexity,