drivers/video: fsl-diu-fb: simplify platforms that have only one port

Allow the platform code not to define a value for diu_ops.set_monitor_port.
This would be for platforms that only have one monitor port.
set_monitor_port() will never be called with an unsupported port anyway.
Signed-off-by: Timur Tabi <timur@freescale.com>

drivers/video/fsl-diu-fb.c

@@ -792,6 +792,7 @@ static void update_lcdc(struct fb_info *info)
 
 	hw = data->diu_reg;
 
+	if (diu_ops.set_monitor_port)
 		diu_ops.set_monitor_port(data->monitor_port);
 	gamma_table_base = data->gamma;