drm/bridge: tc358767: copy the mode data, instead of storing the pointer

In tc_bridge_mode_set callback, we store the pointer to the given
drm_display_mode, and use the mode later. Storing a pointer in such a
way looks very suspicious to me, and I have observed odd issues where
the timings were apparently (at least mostly) zero.

Do a copy of the drm_display_mode instead to ensure we don't refer to
freed/modified data.

Signed-off-by: Tomi Valkeinen <[e-mail]>
Reviewed-by: Andrzej Hajda <[e-mail]>
Signed-off-by: Andrzej Hajda <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/bridge/tc358767.c

···
 	/* display edid */
 	struct edid		*edid;
 	/* current mode */
-	const struct drm_display_mode	*mode;
+	struct drm_display_mode	mode;
 
 	u32			rev;
 	u8			assr;
···
 	/* PXL PLL setup */
 	if (tc_test_pattern) {
 		ret = tc_pxl_pll_en(tc, clk_get_rate(tc->refclk),
-				    1000 * tc->mode->clock);
+				    1000 * tc->mode.clock);
 		if (ret)
 			goto err;
 	}
 
-	ret = tc_set_video_mode(tc, tc->mode);
+	ret = tc_set_video_mode(tc, &tc->mode);
 	if (ret)
 		return ret;
 
···
 {
 	struct tc_data *tc = bridge_to_tc(bridge);
 
-	tc->mode = mode;
+	tc->mode = *mode;
 }
 
 static int tc_connector_get_modes(struct drm_connector *connector)