platform/x86: think-lmi: add missing type attribute

This driver was missing the mandatory type attribute...oops.

Add it in along with logic to determine whether the attribute is an
enumeration type or a string by parsing the possible_values attribute.

Upstream bug https://bugzilla.kernel.org/show_bug.cgi?id=216460

Fixes: a40cd7ef22 ("platform/x86: think-lmi: Add WMI interface support on Lenovo platforms")
Signed-off-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Link: https://lore.kernel.org/r/20230320003221.561750-1-mpearson-lenovo@squebb.ca
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/think-lmi.c

@@ -947,6 +947,20 @@ static ssize_t possible_values_show(struct kobject *kobj, struct kobj_attribute
 	return sysfs_emit(buf, "%s\n", setting->possible_values);
 }
 
+static ssize_t type_show(struct kobject *kobj, struct kobj_attribute *attr,
+		char *buf)
+{
+	struct tlmi_attr_setting *setting = to_tlmi_attr_setting(kobj);
+
+	if (setting->possible_values) {
+		/* Figure out what setting type is as BIOS does not return this */
+		if (strchr(setting->possible_values, ','))
+			return sysfs_emit(buf, "enumeration\n");
+	}
+	/* Anything else is going to be a string */
+	return sysfs_emit(buf, "string\n");
+}
+
 static ssize_t current_value_store(struct kobject *kobj,
 		struct kobj_attribute *attr,
 		const char *buf, size_t count)
@@ -1036,10 +1050,13 @@ static struct kobj_attribute attr_possible_values = __ATTR_RO(possible_values);
 
 static struct kobj_attribute attr_current_val = __ATTR_RW_MODE(current_value, 0600);
 
+static struct kobj_attribute attr_type = __ATTR_RO(type);
+
 static struct attribute *tlmi_attrs[] = {
 	&attr_displ_name.attr,
 	&attr_current_val.attr,
 	&attr_possible_values.attr,
+	&attr_type.attr,
 	NULL
 };