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>
diff --git a/drivers/video/fsl-diu-fb.c b/drivers/video/fsl-diu-fb.c
index ede9e55..5b12e17 100644
--- a/drivers/video/fsl-diu-fb.c
+++ b/drivers/video/fsl-diu-fb.c
@@ -792,7 +792,8 @@
 
 	hw = data->diu_reg;
 
-	diu_ops.set_monitor_port(data->monitor_port);
+	if (diu_ops.set_monitor_port)
+		diu_ops.set_monitor_port(data->monitor_port);
 	gamma_table_base = data->gamma;
 
 	/* Prep for DIU init  - gamma table, cursor table */