[ALSA] Define MPU401 registers in sound/mpu401_uart.h

Define some MPU401 registers in sound/mpu401_uart.h so that other
drivers can refer to them.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/include/sound/mpu401.h b/include/sound/mpu401.h
index d45218b..68b634b 100644
--- a/include/sound/mpu401.h
+++ b/include/sound/mpu401.h
@@ -103,6 +103,21 @@
 #define MPU401D(mpu) (mpu)->port
 
 /*
+ * control register bits
+ */
+/* read MPU401C() */
+#define MPU401_RX_EMPTY		0x80
+#define MPU401_TX_FULL		0x40
+
+/* write MPU401C() */
+#define MPU401_RESET		0xff
+#define MPU401_ENTER_UART	0x3f
+
+/* read MPU401D() */
+#define MPU401_ACK		0xfe
+
+
+/*
 
  */