firmware: arm_scpi: Fix kernel doc warnings

Kernel doc validation script is unhappy and complains with the below set
of warnings.

 | Function parameter or member 'device_domain_id' not described in 'scpi_ops'
 | Function parameter or member 'get_transition_latency' not described in 'scpi_ops'
 | Function parameter or member 'add_opps_to_device' not described in 'scpi_ops'
 | Function parameter or member 'sensor_get_capability' not described in 'scpi_ops'
 | Function parameter or member 'sensor_get_info' not described in 'scpi_ops'
 | Function parameter or member 'sensor_get_value' not described in 'scpi_ops'
 | Function parameter or member 'device_get_power_state' not described in 'scpi_ops'
 | Function parameter or member 'device_set_power_state' not described in 'scpi_ops'

Fix them adding appropriate documents or missing keywords.

Link: https://lore.kernel.org/r/20210712130801.2436492-1-sudeep.holla@arm.comReviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

include/linux/scpi_protocol.h

@@ -51,6 +51,14 @@ struct scpi_sensor_info {
  *	OPP is an index to the list return by @dvfs_get_info
  * @dvfs_get_info: returns the DVFS capabilities of the given power
  *	domain. It includes the OPP list and the latency information
+ * @device_domain_id: gets the scpi domain id for a given device
+ * @get_transition_latency: gets the DVFS transition latency for a given device
+ * @add_opps_to_device: adds all the OPPs for a given device
+ * @sensor_get_capability: get the list of capabilities for the sensors
+ * @sensor_get_info: get the information of the specified sensor
+ * @sensor_get_value: gets the current value of the sensor
+ * @device_get_power_state: gets the power state of a power domain
+ * @device_set_power_state: sets the power state of a power domain
  */
 struct scpi_ops {
 	u32 (*get_version)(void);