Add comprehensive documentation for the RPMsg Ping diagnostic tool,
which is used for testing inter-processor communication and measuring
latency/throughput metrics.
The documentation includes:
- Overview and use cases
- Configuration instructions
- Command syntax and parameters
- Usage examples with sample output
- Architecture workflow diagram
- Best practices for latency and throughput testing
Signed-off-by: Bowen Wang <wangbowen6@xiaomi.com>
bb5eaec973