ASoC: davinci-mcasp: Fix dra7 DMA offset when using CFG port

The TX and RX offset is different for each serializers when using the CFG
port for DMA access.
When using the CFG port only one serializer can be used per direction so
print error message and only configure the first serializer's offset.

Reported-by: Misael Lopez Cruz <misael.lopez@ti.com>
Suggested-by: Misael Lopez Cruz <misael.lopez@ti.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/sound/soc/davinci/davinci-mcasp.h b/sound/soc/davinci/davinci-mcasp.h
index 1e8787f..afddc80 100644
--- a/sound/soc/davinci/davinci-mcasp.h
+++ b/sound/soc/davinci/davinci-mcasp.h
@@ -85,9 +85,9 @@
 						(n << 2))
 
 /* Transmit Buffer for Serializer n */
-#define DAVINCI_MCASP_TXBUF_REG		0x200
+#define DAVINCI_MCASP_TXBUF_REG(n)	(0x200 + (n << 2))
 /* Receive Buffer for Serializer n */
-#define DAVINCI_MCASP_RXBUF_REG		0x280
+#define DAVINCI_MCASP_RXBUF_REG(n)	(0x280 + (n << 2))
 
 /* McASP FIFO Registers */
 #define DAVINCI_MCASP_V2_AFIFO_BASE	(0x1010)