platform/x86: think-lmi: Split current_value to reflect only the value

Currently attributes will show things like:
`BootOrderLock,Disable`
rather than just
`Disable`.

Of course this works, but the attribute is intended to be read by
userspace tools and not require further processing.  That is a userspace
tool can display a drop down of `possible_values` and `current_value` is
one of them from the list.

This also aligns `think-lmi` with how `dell-wmi-sysman` works.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://lore.kernel.org/r/20210622200755.12379-3-mario.limonciello@amd.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Author: superm1

drivers/platform/x86/think-lmi.c

@@ -492,14 +492,19 @@ static ssize_t display_name_show(struct kobject *kobj, struct kobj_attribute *at
 static ssize_t current_value_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
 {
 	struct tlmi_attr_setting *setting = to_tlmi_attr_setting(kobj);
-	char *item;
+	char *item, *value;
 	int ret;
 
 	ret = tlmi_setting(setting->index, &item, LENOVO_BIOS_SETTING_GUID);
 	if (ret)
 		return ret;
 
-	ret = sysfs_emit(buf, "%s\n", item);
+	/* validate and split from `item,value` -> `value` */
+	value = strpbrk(item, ",");
+	if (!value || value == item || !strlen(value + 1))
+		return -EINVAL;
+
+	ret = sysfs_emit(buf, "%s\n", value + 1);
 	kfree(item);
 	return ret;
 }