serial: at91: distinguish usart and uart

Distinguish usart and uart by read ip name register,
The usart read name is "USAR",
The uart and dbgu read name is "DBGU".

Signed-off-by: Elen Song <elen.song@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/include/linux/atmel_serial.h b/include/linux/atmel_serial.h
index fd68337..be201ca 100644
--- a/include/linux/atmel_serial.h
+++ b/include/linux/atmel_serial.h
@@ -124,4 +124,6 @@
 #define ATMEL_US_NER		0x44			/* Number of Errors Register */
 #define ATMEL_US_IF		0x4c			/* IrDA Filter Register */
 
+#define ATMEL_US_NAME		0xf0			/* Ip Name */
+
 #endif