drm/mediatek: Set the default value of rotation to DRM_MODE_ROTATE_0

At the reset hook, call __drm_atomic_helper_plane_reset which is
called at the initialization of the plane and sets the default value of
rotation on all planes to DRM_MODE_ROTATE_0 which is equal to 1.

Tested on Jacuzzi (MTK).
Resolves IGT@kms_properties@plane-properties-{legacy,atomic}
Signed-off-by: Mark Yacoub <markyacoub@chromium.org>
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

drivers/gpu/drm/mediatek/mtk_drm_plane.c

@@ -44,9 +44,10 @@ static void mtk_plane_reset(struct drm_plane *plane)
 		state = kzalloc(sizeof(*state), GFP_KERNEL);
 		if (!state)
 			return;
-		plane->state = &state->base;
 	}
 
+	__drm_atomic_helper_plane_reset(plane, &state->base);
+
 	state->base.plane = plane;
 	state->pending.format = DRM_FORMAT_RGB565;
 }