forked from Mirrors/opensbi

This patch contains the documentation for SBIUnit. It describes: - What is SBIUnit - Simple test writing scenario - How we can cover static functions - How we can "mock" structures in order to test the functions which operate on them - SBIUnit API Reference Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>