Documentation/amdgpu: Modify pp_dpm_*clk details

pp_dpm_*clk nodes also could show the frequencies when a clock is in
'sleep' state. Add documentation related to that.
Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/pm/amdgpu_pm.c

@@ -983,7 +983,15 @@ static ssize_t amdgpu_get_pp_features(struct device *dev,
  * pp_dpm_fclk interface is only available for Vega20 and later ASICs.
  *
  * Reading back the files will show you the available power levels within
- * the power state and the clock information for those levels.
+ * the power state and the clock information for those levels. If deep sleep is
+ * applied to a clock, the level will be denoted by a special level 'S:'
+ * E.g.,
+ *	S: 19Mhz *
+ *	0: 615Mhz
+ *	1: 800Mhz
+ *	2: 888Mhz
+ *	3: 1000Mhz
+ *
  *
  * To manually adjust these states, first select manual using
  * power_dpm_force_performance_level.