ARM: imx: add audio codec clk lookup for imx53-qsb

On imx53-qsb board, the clk ssi_ext.0 is used as the clock input
to audio codec sgtl5000.
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/mach-imx/imx53-dt.c

@@ -10,6 +10,9 @@
  * http://www.gnu.org/copyleft/gpl.html
  */
 
+#include <linux/clk.h>
+#include <linux/clkdev.h>
+#include <linux/err.h>
 #include <linux/io.h>
 #include <linux/irq.h>
 #include <linux/irqdomain.h>
@@ -80,6 +83,19 @@ static const struct of_device_id imx53_iomuxc_of_match[] __initconst = {
 	{ /* sentinel */ }
 };
 
+static void __init imx53_qsb_init(void)
+{
+	struct clk *clk;
+
+	clk = clk_get_sys(NULL, "ssi_ext1");
+	if (IS_ERR(clk)) {
+		pr_err("failed to get clk ssi_ext1\n");
+		return;
+	}
+
+	clk_register_clkdev(clk, NULL, "0-000a");
+}
+
 static void __init imx53_dt_init(void)
 {
 	struct device_node *node;
@@ -96,6 +112,9 @@ static void __init imx53_dt_init(void)
 		of_node_put(node);
 	}
 
+	if (of_machine_is_compatible("fsl,imx53-qsb"))
+		imx53_qsb_init();
+
 	of_platform_populate(NULL, of_default_bus_match_table,
 			     imx53_auxdata_lookup, NULL);
 }