ASoC: Intel: kbl_da7219_max98927: test return value on route add

Fix cppcheck warning:

[sound/soc/intel/boards/kbl_da7219_max98927.c:340] ->
[sound/soc/intel/boards/kbl_da7219_max98927.c:348]: (style) Variable
'ret' is reassigned a value before the old one has been used.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200113210428.27457-7-pierre-louis.bossart@linux.intel.com


Signed-off-by: Mark Brown <broonie@kernel.org>