platform/x86: dell-smbios: only run if proper oem string is detected

The proper way to indicate that a system is a 'supported' Dell System
is by the presence of this string in OEM strings.

Allowing the driver to load on non-Dell systems will have undefined
results.

Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
Reviewed-by: Edward O'Callaghan <quasisec@google.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>

Author: Mario Limonciello

drivers/platform/x86/dell-smbios.c

@@ -172,8 +172,15 @@ static void __init find_tokens(const struct dmi_header *dm, void *dummy)
 
 static int __init dell_smbios_init(void)
 {
+	const struct dmi_device *valid;
 	int ret;
 
+	valid = dmi_find_device(DMI_DEV_TYPE_OEM_STRING, "Dell System", NULL);
+	if (!valid) {
+		pr_err("Unable to run on non-Dell system\n");
+		return -ENODEV;
+	}
+
 	dmi_walk(find_tokens, NULL);
 
 	if (!da_tokens)  {