[ALSA] Add MPU401_INFO_NO_ACK bitflag

Added MPU401_INFO_NO_ACK bitflag to ignore the ACK check for UART
commands.  VT172x doesn't handle ACK commands, for example.

Tested-by: Pavel Hofman <pavel.hofman@insite.cz>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/include/sound/mpu401.h b/include/sound/mpu401.h
index 68b634b..1f1d53f 100644
--- a/include/sound/mpu401.h
+++ b/include/sound/mpu401.h
@@ -50,6 +50,7 @@
 #define MPU401_INFO_INTEGRATED	(1 << 2)	/* integrated h/w port */
 #define MPU401_INFO_MMIO	(1 << 3)	/* MMIO access */
 #define MPU401_INFO_TX_IRQ	(1 << 4)	/* independent TX irq */
+#define MPU401_INFO_NO_ACK	(1 << 6)	/* No ACK cmd needed */
 
 #define MPU401_MODE_BIT_INPUT		0
 #define MPU401_MODE_BIT_OUTPUT		1