ASoC: soc-pcm: add error log

ASoC: soc-pcm: add error log

cppcheck warning:

sound/soc/soc-pcm.c:1907:6: style: Variable 'err' is assigned a value
that is never used. [unreadVariable]
 err = dpcm_be_dai_hw_free(fe, stream);
     ^

it's not clear why dpcm_be_dai_hw_free() is sometimes called without
testing the error status, and sometimes an error message is provided.

When in doubt, add an error message for consistency. This may have to
be revisited.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20210218221921.88991-5-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>