ASoC: Intel: Skylake: Make local functions static

Some functions are local to the source and do not need to be in global
scope, so make them static.

Signed-off-by: Guneshwor Singh <guneshwor.o.singh@intel.com>
Acked-By: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/skylake/skl.c

@@ -545,7 +545,7 @@ struct skl_clk_parent_src *skl_get_parent_clk(u8 clk_id)
 	return NULL;
 }
 
-void init_skl_xtal_rate(int pci_id)
+static void init_skl_xtal_rate(int pci_id)
 {
 	switch (pci_id) {
 	case 0x9d70: