ASoC: lpass-platform: initialize dma channel number

A bugfix accidentally removed the implicit initialization of the
dma channel number, causing undefined behavior when
v->alloc_dma_channel is NULL:

sound/soc/qcom/lpass-platform.c: In function ‘lpass_platform_pcmops_open’:
sound/soc/qcom/lpass-platform.c:83:29: error: ‘dma_ch’ may be used uninitialized in this function [-Werror=maybe-uninitialized]

This adds back an explicit initialization to zero, restoring the
previous behavior for that case.

Fixes: 022d00ee ("ASoC: lpass-platform: Fix broken pcm data usage")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kenneth Westfield <kwestfie@codeaurora.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/qcom/lpass-platform.c

@@ -77,6 +77,9 @@ static int lpass_platform_pcmops_open(struct snd_pcm_substream *substream)
 
 	if (v->alloc_dma_channel)
 		dma_ch = v->alloc_dma_channel(drvdata, dir);
+	else
+		dma_ch = 0;
+
 	if (dma_ch < 0)
 		return dma_ch;