module: update and fix documentation on SCMI and power distributor

- Updated the module name to "Power Budget Distributor" in
`power_distributor.md`.
- Added `MOD_SCMI_PROTOCOL_DAYNAMIC_PAYLOAD_SIZE` to define the
maximum dynamic payload size in `mod_scmi_std`.
- Fixed comment formatting for the `state_table` pointer
in `mod_scmi_clock.h`.
- Fixed a missing closing documentation block in
`mod_scmi_telemetry.h`.

Signed-off-by: Leandro Belli <leandro.belli@arm.com>