drm/panel: visionox-rm69299: Don't clear all mode flags

Don't clear all mode flags. We only want to maek sure we use HS mode
during unprepare.

Fixes: c7f66d3 ("drm/panel: add support for rm69299 visionox panel")
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Guido Günther <agx@sigxcpu.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20250910-shift6mq-panel-v3-2-a7729911afb9@sigxcpu.org

Author: agx

drivers/gpu/drm/panel/panel-visionox-rm69299.c

@@ -192,7 +192,7 @@ static int visionox_rm69299_unprepare(struct drm_panel *panel)
 	struct visionox_rm69299 *ctx = panel_to_ctx(panel);
 	struct mipi_dsi_multi_context dsi_ctx = { .dsi = ctx->dsi };
 
-	ctx->dsi->mode_flags = 0;
+	ctx->dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
 
 	mipi_dsi_dcs_set_display_off_multi(&dsi_ctx);