[PATCH v1] scmi_protocols: Update discover list protocol message

[Fabio Estevam]

Hi Alice and NXP folks,

> Changing a constant from 3 to 4 isn't good, please define something and
> add a comment explaining what the constant means so it'll be clear
> when/why someone changes it to 5. Thanks.

Please improve all the commit messages from the recent patches.

All patches need a clear commit log explaining the
motivation/rationale for the change.

The recent patches have poor commit messages and we cannot take them as-is.

Thanks