firmware: arm_scmi: Fix kernel doc warnings

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

 | Function parameter or member 'fast_switch_possible' not described in 'scmi_perf_proto_ops'
 | Function parameter or member 'power_scale_mw_get' not described in 'scmi_perf_proto_ops'
 | cannot understand function prototype: 'struct scmi_sensor_reading '
 | cannot understand function prototype: 'struct scmi_range_attrs '
 | cannot understand function prototype: 'struct scmi_sensor_axis_info '
 | cannot understand function prototype: 'struct scmi_sensor_intervals_info '

Fix them adding appropriate documents or missing keywords.

Link: https://lore.kernel.org/r/20210712130801.2436492-2-sudeep.holla@arm.comReviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

include/linux/scmi_protocol.h

@@ -101,6 +101,10 @@ struct scmi_clk_proto_ops {
  *	to sustained performance level mapping
  * @est_power_get: gets the estimated power cost for a given performance domain
  *	at a given frequency
+ * @fast_switch_possible: indicates if fast DVFS switching is possible or not
+ *	for a given device
+ * @power_scale_mw_get: indicates if the power values provided are in milliWatts
+ *	or in some other (abstract) scale
  */
 struct scmi_perf_proto_ops {
 	int (*limits_set)(const struct scmi_protocol_handle *ph, u32 domain,
@@ -153,7 +157,7 @@ struct scmi_power_proto_ops {
 };
 
 /**
- * scmi_sensor_reading  - represent a timestamped read
+ * struct scmi_sensor_reading  - represent a timestamped read
  *
  * Used by @reading_get_timestamped method.
  *
@@ -167,7 +171,7 @@ struct scmi_sensor_reading {
 };
 
 /**
- * scmi_range_attrs  - specifies a sensor or axis values' range
+ * struct scmi_range_attrs  - specifies a sensor or axis values' range
  * @min_range: The minimum value which can be represented by the sensor/axis.
  * @max_range: The maximum value which can be represented by the sensor/axis.
  */
@@ -177,7 +181,7 @@ struct scmi_range_attrs {
 };
 
 /**
- * scmi_sensor_axis_info  - describes one sensor axes
+ * struct scmi_sensor_axis_info  - describes one sensor axes
  * @id: The axes ID.
  * @type: Axes type. Chosen amongst one of @enum scmi_sensor_class.
  * @scale: Power-of-10 multiplier applied to the axis unit.
@@ -205,8 +209,8 @@ struct scmi_sensor_axis_info {
 };
 
 /**
- * scmi_sensor_intervals_info  - describes number and type of available update
- * intervals
+ * struct scmi_sensor_intervals_info  - describes number and type of available
+ *	update intervals
  * @segmented: Flag for segmented intervals' representation. When True there
  *	       will be exactly 3 intervals in @desc, with each entry
  *	       representing a member of a segment in this order: