usb: gadget: start with libcomposite

This patch aims to be simple. It removes #include usbstribgs.c line from each
gadget and creates libcomposite.ko which has only one member, that is
usbstribgs.c.

Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/gadget/usbstring.c b/drivers/usb/gadget/usbstring.c
index 4d25b90..24e9bbd 100644
--- a/drivers/usb/gadget/usbstring.c
+++ b/drivers/usb/gadget/usbstring.c
@@ -9,6 +9,7 @@
 
 #include <linux/errno.h>
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/list.h>
 #include <linux/string.h>
 #include <linux/device.h>
@@ -68,4 +69,5 @@
 	buf [1] = USB_DT_STRING;
 	return buf [0];
 }
-
+EXPORT_SYMBOL_GPL(usb_gadget_get_string);
+MODULE_LICENSE("GPL");