drm/amd/amdgpu/amdgpu_drv.c: Replace drm_modeset_lock_all with drm_modeset_lock

drm_modeset_lock_all() is not needed here, so it is replaced with
drm_modeset_lock(). The crtc list around which we are looping never
changes, therefore the only lock we need is to protect access to
crtc->state.
Suggested-by: NDaniel Vetter <daniel@ffwll.ch>
Suggested-by: NMatthew Wilcox <willy@infradead.org>
Signed-off-by: NFabio M. De Francesco <fmdefrancesco@gmail.com>
Reviewed-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c

@@ -1599,17 +1599,15 @@ static int amdgpu_pmops_runtime_idle(struct device *dev)
 	if (amdgpu_device_has_dc_support(adev)) {
 		struct drm_crtc *crtc;
 
-		drm_modeset_lock_all(drm_dev);
-
 		drm_for_each_crtc(crtc, drm_dev) {
-			if (crtc->state->active) {
+			drm_modeset_lock(&crtc->mutex, NULL);
+			if (crtc->state->active)
 				ret = -EBUSY;
+			drm_modeset_unlock(&crtc->mutex);
+			if (ret < 0)
 				break;
-			}
 		}
 
-		drm_modeset_unlock_all(drm_dev);
-
 	} else {
 		struct drm_connector *list_connector;
 		struct drm_connector_list_iter iter;