Use drm_gem_object_[handle_]unreference_unlocked where possible

Mostly obvious simplifications.

The i915 pread/pwrite ioctls, intel_overlay_put_image and
nouveau_gem_new were incorrectly using the locked versions
without locking: this is also fixed in this patch.

Signed-off-by: Luca Barbieri <luca@luca-barbieri.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 12775df..8f72d0b 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -3434,11 +3434,10 @@
 	intel_crtc->cursor_bo = bo;
 
 	return 0;
-fail:
-	mutex_lock(&dev->struct_mutex);
 fail_locked:
-	drm_gem_object_unreference(bo);
 	mutex_unlock(&dev->struct_mutex);
+fail:
+	drm_gem_object_unreference_unlocked(bo);
 	return ret;
 }
 
@@ -4351,9 +4350,7 @@
 		intelfb_remove(dev, fb);
 
 	drm_framebuffer_cleanup(fb);
-	mutex_lock(&dev->struct_mutex);
-	drm_gem_object_unreference(intel_fb->obj);
-	mutex_unlock(&dev->struct_mutex);
+	drm_gem_object_unreference_unlocked(intel_fb->obj);
 
 	kfree(intel_fb);
 }
@@ -4416,9 +4413,7 @@
 
 	ret = intel_framebuffer_create(dev, mode_cmd, &fb, obj);
 	if (ret) {
-		mutex_lock(&dev->struct_mutex);
-		drm_gem_object_unreference(obj);
-		mutex_unlock(&dev->struct_mutex);
+		drm_gem_object_unreference_unlocked(obj);
 		return NULL;
 	}