ASoC: mediatek: mtk-btcvsd: remove useless assignment

cppcheck warning:

sound/soc/mediatek/common/mtk-btcvsd.c:783:34: style: Variable 'avail'
is assigned a value that is never used. [unreadVariable]
 int written_size = count, avail = 0, cur_write_idx, write_size, cont;
                                 ^
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20210311004904.121205-2-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/mediatek/common/mtk-btcvsd.c

@@ -780,7 +780,7 @@ static ssize_t mtk_btcvsd_snd_write(struct mtk_btcvsd_snd *bt,
 				    char __user *buf,
 				    size_t count)
 {
-	int written_size = count, avail = 0, cur_write_idx, write_size, cont;
+	int written_size = count, avail, cur_write_idx, write_size, cont;
 	unsigned int cur_buf_ofs = 0;
 	unsigned long flags;
 	unsigned int packet_size = bt->tx->packet_size;