ASoC: intel - atom: statify sst_slot_enum_info

Sparse complains that sst_slot_enum_info should be static, so make it
static

sound/soc/intel/atom/sst-atom-controls.c:135:5: warning: symbol
'sst_slot_enum_info' was not declared. Should it be static?

Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Acked-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/atom/sst-atom-controls.c

@@ -132,7 +132,7 @@ static int sst_send_slot_map(struct sst_data *drv)
 			      sizeof(cmd.header) + cmd.header.length);
 }
 
-int sst_slot_enum_info(struct snd_kcontrol *kcontrol,
+static int sst_slot_enum_info(struct snd_kcontrol *kcontrol,
 		       struct snd_ctl_elem_info *uinfo)
 {
 	struct sst_enum *e = (struct sst_enum *)kcontrol->private_value;