drm/omap: verify that display x-res is divisible by 8

DISPC requires the x resolution to be divisible by 8 when stall mode is
not used.

Add a check to the DPI driver to verify this.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>

drivers/gpu/drm/omapdrm/dss/dpi.c

@@ -513,6 +513,9 @@ static int dpi_check_timings(struct omap_dss_device *dssdev,
 	struct dpi_clk_calc_ctx ctx;
 	bool ok;
 
+	if (timings->x_res % 8 != 0)
+		return -EINVAL;
+
 	if (mgr && !dispc_mgr_timings_ok(mgr->id, timings))
 		return -EINVAL;