drm/panel: visionox-rm69299: Fix clock frequency for SHIFT6mq

Make the clock frequency match what the sdm845 downstream kernel
uses. Otherwise the panel stays black.

Fixes: 783334f ("drm/panel: visionox-rm69299: support the variant found in the SHIFT6mq")
Signed-off-by: Guido Günther <agx@sigxcpu.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.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-v3-1-a7729911afb9@sigxcpu.org

Author: agx

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

@@ -247,7 +247,7 @@ static const struct drm_display_mode visionox_rm69299_1080x2248_60hz = {
 };
 
 static const struct drm_display_mode visionox_rm69299_1080x2160_60hz = {
-	.clock = 158695,
+	.clock = (2160 + 8 + 4 + 4) * (1080 + 26 + 2 + 36) * 60 / 1000,
 	.hdisplay = 1080,
 	.hsync_start = 1080 + 26,
 	.hsync_end = 1080 + 26 + 2,