dm: sound: Create a uclass for i2s

The i2s bus is commonly used with audio codecs. It provides a way to
stream digital data sychronously in both directions. U-Boot only supports
audio output, so this uclass is very simple, with a single tx_data()
method.

Add a uclass and a test for i2s.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/i2s.h b/include/i2s.h
index f23862c..28f6184 100644
--- a/include/i2s.h
+++ b/include/i2s.h
@@ -87,17 +87,41 @@
 	unsigned int id;		/* I2S controller id */
 };
 
+/* Operations for i2s devices */
+struct i2s_ops {
+	/**
+	 * tx_data() - Transmit audio data
+	 *
+	 * @dev: I2C device
+	 * @data: Data buffer to play
+	 * @data_size: Size of data buffer in bytes
+	 * @return 0 if OK, -ve on error
+	 */
+	int (*tx_data)(struct udevice *dev, void *data, uint data_size);
+};
+
+#define i2s_get_ops(dev)	((struct i2s_ops *)(dev)->driver->ops)
+
+/**
+ * i2s_tx_data() - Transmit audio data
+ *
+ * @dev: I2C device
+ * @data: Data buffer to play
+ * @data_size: Size of data buffer in bytes
+ * @return 0 if OK, -ve on error
+ */
+int i2s_tx_data(struct udevice *dev, void *data, uint data_size);
+
 /*
  * Sends the given data through i2s tx
  *
  * @param pi2s_tx	pointer of i2s transmitter parameter structure.
  * @param data		address of the data buffer
- * @param data_size	array size of the int buffer (total size / size of int)
- *
+ * @param data_size	size of the data (in bytes)
  * @return		int value 0 for success, -1 in case of error
  */
-int i2s_transfer_tx_data(struct i2s_uc_priv *pi2s_tx, unsigned int *data,
-			 unsigned long data_size);
+int i2s_transfer_tx_data(struct i2s_uc_priv *pi2s_tx, void *data,
+			 uint data_size);
 
 /*
  * Initialise i2s transmiter