imx-drm: ipu-di: Check the return value from clk_prepare_enable()

clk_prepare_enable() may fail, so let's check its return value and propagate it
in the case of error.
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>
Acked-by: NSascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/imx-drm/ipu-v3/ipu-di.c

@@ -654,7 +654,9 @@ EXPORT_SYMBOL_GPL(ipu_di_init_sync_panel);
 
 int ipu_di_enable(struct ipu_di *di)
 {
-	clk_prepare_enable(di->clk_di_pixel);
+	int ret = clk_prepare_enable(di->clk_di_pixel);
+	if (ret)
+		return ret;
 
 	ipu_module_enable(di->ipu, di->module);