ASoC: soc-pcm: indicate error message at dpcm_be_dai_trigger()

Indicating error message when failed case is very useful for debuging.
In many case, its style is like below.

	int function(...)
	{
		...
		return ret;
	}

	int caller(...)
	{
		...
		ret = function(...);
		if (ret < 0)
			dev_err(...)
		...
	}

This is not so bad, but in this style *each caller* needs to indicate
duplicate same error message, and some caller is forgetting to do it.
And caller can't indicate detail function() error information.

If function() indicates error message, we can get same and
detail information without forgot.

	int function(...)
	{
		...
		if (ret < 0)
			dev_err(...)

		return ret;
	}

	int caller(...)
	{
		...
		ret = function(...);
		...
	}

Now, dpcm_be_dai_trigger() user uses it like below.

	err = dpcm_be_dai_trigger(...);
	if (err < 0)
		dev_err(..., "ASoC: trigger FE failed %d\n", err);

But we can get more detail information if dpcm_be_dai_trigger() itself
had dev_err(). And above error message is confusable,
failed is *BE*, not *FE*.

This patch indicates error message at dpcm_be_dai_trigger().

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87lfaputbe.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>