drm/msm/dpu: drop unused dpu_plane::lock

The field dpu_plane::lock was never used for protecting any kind of
data. Drop it now.
Reviewed-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/570043/
Link: https://lore.kernel.org/r/20231201211845.1026967-8-dmitry.baryshkov@linaro.org

drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c

@@ -78,8 +78,6 @@ static const uint32_t qcom_compressed_supported_formats[] = {
 struct dpu_plane {
 	struct drm_plane base;
 
-	struct mutex lock;
-
 	enum dpu_sspp pipe;
 
 	uint32_t color_fill;
@@ -1230,8 +1228,6 @@ static void dpu_plane_destroy(struct drm_plane *plane)
 		if (pstate->r_pipe.sspp)
 			_dpu_plane_set_qos_ctrl(plane, &pstate->r_pipe, false);
 
-		mutex_destroy(&pdpu->lock);
-
 		/* this will destroy the states as well */
 		drm_plane_cleanup(plane);
 
@@ -1491,8 +1487,6 @@ struct drm_plane *dpu_plane_init(struct drm_device *dev,
 	/* success! finalize initialization */
 	drm_plane_helper_add(plane, &dpu_plane_helper_funcs);
 
-	mutex_init(&pdpu->lock);
-
 	DPU_DEBUG("%s created for pipe:%u id:%u\n", plane->name,
 					pipe, plane->base.id);
 	return plane;