ALSA: control: Define SNDRV_CTL_TLV_OP_* constants

Instead of hard-coded magic numbers, define constants for op_flag to
tlv callbacks.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/core/control.c b/sound/core/control.c
index f0b0e14..b961134 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -1406,11 +1406,11 @@
 	case SNDRV_CTL_IOCTL_SUBSCRIBE_EVENTS:
 		return snd_ctl_subscribe_events(ctl, ip);
 	case SNDRV_CTL_IOCTL_TLV_READ:
-		return snd_ctl_tlv_ioctl(ctl, argp, 0);
+		return snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_READ);
 	case SNDRV_CTL_IOCTL_TLV_WRITE:
-		return snd_ctl_tlv_ioctl(ctl, argp, 1);
+		return snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_WRITE);
 	case SNDRV_CTL_IOCTL_TLV_COMMAND:
-		return snd_ctl_tlv_ioctl(ctl, argp, -1);
+		return snd_ctl_tlv_ioctl(ctl, argp, SNDRV_CTL_TLV_OP_CMD);
 	case SNDRV_CTL_IOCTL_POWER:
 		return -ENOPROTOOPT;
 	case SNDRV_CTL_IOCTL_POWER_STATE: