drivers/generic/max98357a: Add extra error handling

It is possible that acpi_device_scope() and acpi_device_name() can
return NULL to indicate an error, so add error handling to check their
return values.

Change-Id: I4c7ab0c592845d9d5f142e078fc2b505a99ecd12
Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
Found-by: Coverity CID 1362592
Reviewed-on: https://review.coreboot.org/c/coreboot/+/33028
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
diff --git a/src/drivers/generic/max98357a/max98357a.c b/src/drivers/generic/max98357a/max98357a.c
index 1408dac..838491d 100644
--- a/src/drivers/generic/max98357a/max98357a.c
+++ b/src/drivers/generic/max98357a/max98357a.c
@@ -36,9 +36,14 @@
 	if (!dev->enabled || !config)
 		return;
 
+	const char *scope = acpi_device_scope(dev);
+	const char *name = acpi_device_name(dev);
+	if (!scope || !name)
+		return;
+
 	/* Device */
-	acpigen_write_scope(acpi_device_scope(dev));
-	acpigen_write_device(acpi_device_name(dev));
+	acpigen_write_scope(scope);
+	acpigen_write_device(name);
 	acpigen_write_name_string("_HID", MAX98357A_ACPI_HID);
 	acpigen_write_name_integer("_UID", 0);
 	acpigen_write_name_string("_DDN", dev->chip_ops->name);