platform/x86: wmi: move struct wmi_device_id to mod_devicetable.h

In preparation for adding WMI support to MODULE_DEVICE_TABLE() move the
definition of struct wmi_device_id to mod_devicetable.h and inline
guid_string in the struct.

Changing guid_string to an inline char array changes the loop conditions
when looping over an array of struct wmi_device_id. Therefore update
wmi_dev_match()'s loop to check for an empty guid_string instead of a
NULL pointer.

Signed-off-by: Mattias Jacobsson <2pi@mok.nu>
[dvhart: Move UUID_STRING_LEN define to this patch]
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>
diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
index f9bd2f3..e44b90f 100644
--- a/include/linux/mod_devicetable.h
+++ b/include/linux/mod_devicetable.h
@@ -779,4 +779,16 @@ struct typec_device_id {
 	kernel_ulong_t driver_data;
 };
 
+/* WMI */
+
+#define WMI_MODULE_PREFIX	"wmi:"
+
+/**
+ * struct wmi_device_id - WMI device identifier
+ * @guid_string: 36 char string of the form fa50ff2b-f2e8-45de-83fa-65417f2f49ba
+ */
+struct wmi_device_id {
+	const char guid_string[UUID_STRING_LEN+1];
+};
+
 #endif /* LINUX_MOD_DEVICETABLE_H */