drm/amd/pm/swsmu/smu11/vangogh_ppt: Provide a couple of missing parameter descriptions

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/amd/amdgpu/../pm/swsmu/smu11/vangogh_ppt.c:2381: warning: Function parameter or member 'residency' not described in 'vangogh_get_gfxoff_residency'
 drivers/gpu/drm/amd/amdgpu/../pm/swsmu/smu11/vangogh_ppt.c:2399: warning: Function parameter or member 'entrycount' not described in 'vangogh_get_gfxoff_entrycount'

Cc: Evan Quan <evan.quan@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: "Pan, Xinhui" <Xinhui.Pan@amd.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Li Ma <li.ma@amd.com>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/pm/swsmu/smu11/vangogh_ppt.c

@@ -2389,6 +2389,7 @@ static u32 vangogh_set_gfxoff_residency(struct smu_context *smu, bool start)
  * vangogh_get_gfxoff_residency
  *
  * @smu: amdgpu_device pointer
+ * @residency: placeholder for return value
  *
  * This function will be used to get gfxoff residency.
  *
@@ -2407,6 +2408,7 @@ static u32 vangogh_get_gfxoff_residency(struct smu_context *smu, uint32_t *resid
  * vangogh_get_gfxoff_entrycount - get gfxoff entry count
  *
  * @smu: amdgpu_device pointer
+ * @entrycount: placeholder for return value
  *
  * This function will be used to get gfxoff entry count
  *