ASoC: Intel: skl_nau88l25_max98357a: rename shadowed variable

ASoC: Intel: skl_nau88l25_max98357a: rename shadowed variable

Fix cppcheck warning:

[sound/soc/intel/boards/skl_nau88l25_max98357a.c:257] ->
[sound/soc/intel/boards/skl_nau88l25_max98357a.c:142]: (style) Local
variable 'channels' shadows outer variable

[sound/soc/intel/boards/skl_nau88l25_max98357a.c:257] ->
[sound/soc/intel/boards/skl_nau88l25_max98357a.c:318]: (style) Local
variable 'channels' shadows outer variable

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200113210428.27457-14-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>