[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>

include/sound/mpu401.h

@@ -102,6 +102,21 @@ struct snd_mpu401 {
 #define MPU401C(mpu) (mpu)->cport
 #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
+
+
 /*
 
  */