dm: usb: Move struct usb_string to a common place

This is needed for sandbox USB device emulation, so move it to a place
where it can be found by things other than gadgets.
Signed-off-by: NSimon Glass <sjg@chromium.org>
Reviewed-by: NMarek Vasut <marex@denx.de>

include/linux/usb/ch9.h

@@ -1002,4 +1002,17 @@ struct usb_set_sel_req {
  */
 #define USB_SELF_POWER_VBUS_MAX_DRAW		100
 
+/**
+ * struct usb_string - wraps a C string and its USB id
+ * @id:the (nonzero) ID for this string
+ * @s:the string, in UTF-8 encoding
+ *
+ * If you're using usb_gadget_get_string(), use this to wrap a string
+ * together with its ID.
+ */
+struct usb_string {
+	u8 id;
+	const char *s;
+};
+
 #endif /* __LINUX_USB_CH9_H */

include/linux/usb/gadget.h

@@ -858,19 +858,6 @@ void usb_del_gadget_udc(struct usb_gadget *gadget);
 
 /* utility to simplify dealing with string descriptors */
 
-/**
- * struct usb_string - wraps a C string and its USB id
- * @id:the (nonzero) ID for this string
- * @s:the string, in UTF-8 encoding
- *
- * If you're using usb_gadget_get_string(), use this to wrap a string
- * together with its ID.
- */
-struct usb_string {
-	u8			id;
-	const char		*s;
-};
-
 /**
  * struct usb_gadget_strings - a set of USB strings in a given language
  * @language:identifies the strings' language (0x0409 for en-us)