ASoC: samsung: i2s: Document clocks macros

Document clocks macros with their description
from 'Documentation/devicetree/bindings/sound/samsung-i2s.txt'
Signed-off-by: Maciej Falkowski <m.falkowski@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>

include/dt-bindings/sound/samsung-i2s.h

@@ -2,8 +2,14 @@
 #ifndef _DT_BINDINGS_SAMSUNG_I2S_H
 #define _DT_BINDINGS_SAMSUNG_I2S_H
 
-#define CLK_I2S_CDCLK		0
-#define CLK_I2S_RCLK_SRC	1
-#define CLK_I2S_RCLK_PSR	2
+#define CLK_I2S_CDCLK		0 /* the CDCLK (CODECLKO) gate clock */
+
+#define CLK_I2S_RCLK_SRC	1 /* the RCLKSRC mux clock (corresponding to
+				   * RCLKSRC bit in IISMOD register)
+				   */
+
+#define CLK_I2S_RCLK_PSR	2 /* the RCLK prescaler divider clock
+				   * (corresponding to the IISPSR register)
+				   */
 
 #endif /* _DT_BINDINGS_SAMSUNG_I2S_H */