ARM: at91: atmel-ssc: add device tree support

Add atmel-ssc for device tree support

Match "atmel,at91rm9200-ssc" for using pdc for data transfer
Match "atmel,at91sam9g45-ssc" for using dma for data transfer

Signed-off-by: Bo Shen <voice.shen@atmel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

Documentation/devicetree/bindings/misc/atmel-ssc.txt

@@ -0,0 +1,15 @@
+* Atmel SSC driver.
+
+Required properties:
+- compatible: "atmel,at91rm9200-ssc" or "atmel,at91sam9g45-ssc"
+	- atmel,at91rm9200-ssc: support pdc transfer
+	- atmel,at91sam9g45-ssc: support dma transfer
+- reg: Should contain SSC registers location and length
+- interrupts: Should contain SSC interrupt
+
+Example:
+ssc0: ssc@fffbc000 {
+	compatible = "atmel,at91rm9200-ssc";
+	reg = <0xfffbc000 0x4000>;
+	interrupts = <14 4 5>;
+};