asoc/multi-component: fsl: add support for disabled SSI nodes

Add support for adding "status = disabled" to an SSI node to incidate that it
is not wired on the board.  This replaces the not-so-intuitive previous method
of omitting a codec-handle property.
Signed-off-by: Timur Tabi <timur@freescale.com>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>

arch/powerpc/boot/dts/mpc8610_hpcd.dts

@@ -286,6 +286,7 @@ ssi@16000 {
 
 		ssi@16100 {
 			compatible = "fsl,mpc8610-ssi";
+			status = "disabled";
 			cell-index = <1>;
 			reg = <0x16100 0x100>;
 			interrupt-parent = <&mpic>;

sound/soc/fsl/fsl_ssi.c

@@ -625,12 +625,19 @@ static int __devinit fsl_ssi_probe(struct of_device *of_dev,
 	struct resource res;
 	char name[64];
 
-	/* We are only interested in SSIs with a codec phandle in them, so let's
-	 * make sure this SSI has one.
+	/* SSIs that are not connected on the board should have a
+	 *      status = "disabled"
+	 * property in their device tree nodes.
 	 */
-	if (!of_get_property(np, "codec-handle", NULL))
+	if (!of_device_is_available(np))
 		return -ENODEV;
 
+	/* Check for a codec-handle property. */
+	if (!of_get_property(np, "codec-handle", NULL)) {
+		dev_err(&of_dev->dev, "missing codec-handle property\n");
+		return -ENODEV;
+	}
+
 	/* We only support the SSI in "I2S Slave" mode */
 	sprop = of_get_property(np, "fsl,mode", NULL);
 	if (!sprop || strcmp(sprop, "i2s-slave")) {