firmware: arm_scmi: Align few names in sensors protocol with SCMI specification

Looks like more code developed during the draft versions of the
specification slipped through and they don't match the final
released version. This seem to have happened only with sensor
protocol.

Renaming few command and function names here to match exactly with
the released version of SCMI specification for ease of maintenance.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>