ASoC: Intel: atom: statify cht_quirk

Sparse rightly warns:
sound/soc/intel/atom/sst/sst_acpi.c:353:22: warning: symbol 'cht_quirk' was not declared. Should it be static?

So statify this

Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>