ASoC: Intel: boards: add 'static' qualifiers for max98390 routes

ASoC: Intel: boards: add 'static' qualifiers for max98390 routes

Sparse warnings:

sound/soc/intel/boards/sof_maxim_common.c:140:33: error: symbol
'max_98390_dapm_routes' was not declared. Should it be static?

sound/soc/intel/boards/sof_maxim_common.c:156:33: error: symbol
'max_98390_tt_dapm_routes' was not declared. Should it be static?

Fixes: f316c9d9ba8ea ('ASoC: Intel: boards: add max98390 2/4 speakers support')
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20211207211700.115319-1-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>