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>

sound/soc/intel/atom/sst/sst_acpi.c

@@ -350,7 +350,7 @@ static struct sst_acpi_mach cht_surface_mach = {
 	"10EC5640", "cht-bsw-rt5645", "intel/fw_sst_22a8.bin", "cht-bsw", NULL,
 								&chv_platform_data };
 
-struct sst_acpi_mach *cht_quirk(void *arg)
+static struct sst_acpi_mach *cht_quirk(void *arg)
 {
 	struct sst_acpi_mach *mach = arg;