drm/omap: fix WBDELAYCOUNT for HDMI

For HDMI, WBDELAYCOUNT starts counting at the start of vsync, not at the
start of vfp.

This patch adjusts the wbdelay for HDMI accordingly.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

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

@@ -2816,6 +2816,10 @@ int dispc_wb_setup(struct dispc_device *dispc,
 	} else {
 		int wbdelay;
 
+		if (channel_in == DSS_WB_TV_MGR)
+			wbdelay = min(vm->vsync_len + vm->vback_porch,
+				(u32)255);
+		else
 			wbdelay = min(vm->vfront_porch +
 				vm->vsync_len + vm->vback_porch, (u32)255);