ALSA: firewire-lib: use union for directional parameters

Some parameters of struct amdtp_stream is dependent on direction.

This commit uses union for such parameters to distinguish from
common parameters.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/fireworks/fireworks_stream.c

@@ -165,13 +165,13 @@ int snd_efw_stream_init_duplex(struct snd_efw *efw)
 	    (efw->firmware_version == 0x5070000 ||
 	     efw->firmware_version == 0x5070300 ||
 	     efw->firmware_version == 0x5080000))
-		efw->tx_stream.tx_first_dbc = 0x02;
+		efw->tx_stream.ctx_data.tx.first_dbc = 0x02;
 	/* AudioFire9 always reports wrong dbs. */
 	if (efw->is_af9)
 		efw->tx_stream.flags |= CIP_WRONG_DBS;
 	/* Firmware version 5.5 reports fixed interval for dbc. */
 	if (efw->firmware_version == 0x5050000)
-		efw->tx_stream.tx_dbc_interval = 8;
+		efw->tx_stream.ctx_data.tx.dbc_interval = 8;
 
 	err = init_stream(efw, &efw->rx_stream);
 	if (err < 0) {