soc/intel/cannonlake: Fix Coverity scan error

Add return in case of null pointer to avoid coverity scan error, fixed
  1.Coverity ID 1379849:  Null pointer dereferences  (FORWARD_NULL)
  2.Coverity ID 1379848:  Null pointer dereferences  (FORWARD_NULL)

Change-Id: Ica19735307736c8a55c29af88db8b1372f8779e4
Signed-off-by: Lijian Zhao <lijian.zhao@intel.com>
Reviewed-on: https://review.coreboot.org/21155
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Pratikkumar V Prajapati <pratikkumar.v.prajapati@intel.com>

src/soc/intel/cannonlake/pmutil.c

@@ -207,6 +207,7 @@ void soc_get_gpe_configs(uint8_t *dw0, uint8_t *dw1, uint8_t *dw2)
 	DEVTREE_CONST struct device *dev = dev_find_slot(0, PCH_DEVFN_PMC);
 	if (!dev || !dev->chip_info) {
 		printk(BIOS_ERR, "BUG! Could not find SOC devicetree config\n");
+		return;
 	}
 	config = dev->chip_info;