superio/nuvoton: Avoid NULL pointer dereference

Coverity detects dereferencing a pointer that might be "NULL" when
calling acpigen_write_scope. Add sanity check for scope to prevent
NULL pointer dereference.

Found-by: Coverity CID 1420207

Signed-off-by: John Zhao <john.zhao@intel.com>
Change-Id: Icc253c63aadef1c0ecb116a38b608f64f80abc79
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42839
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
diff --git a/src/superio/nuvoton/npcd378/superio.c b/src/superio/nuvoton/npcd378/superio.c
index 628bd4e..b7f98af 100644
--- a/src/superio/nuvoton/npcd378/superio.c
+++ b/src/superio/nuvoton/npcd378/superio.c
@@ -325,7 +325,11 @@
 	acpigen_pop_len();		/* Pop Scope */
 
 	/* Inject into parent: */
-	acpigen_write_scope(acpi_device_scope(dev));
+	if (!scope) {
+		printk(BIOS_ERR, "%s: Missing ACPI path/scope\n", dev_path(dev));
+		return;
+	}
+	acpigen_write_scope(scope);
 
 	acpigen_write_name_integer("MSFG", 1);
 	acpigen_write_name_integer("KBFG", 1);
@@ -404,6 +408,9 @@
 
 static void npcd378_fill_ssdt_generator(const struct device *dev)
 {
+	if (!dev)
+		return;
+
 	superio_common_fill_ssdt_generator(dev);
 
 	switch (dev->path.pnp.device) {