usb, g_dnl: make possibility to fixup the device_desc board specific

add a weak dummy function g_dnl_fixup to add the possibility to update
the device_desc board specific. Used on the upcoming siemens board
support, where idVendor and idProduct is stored in an eeprom.

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Marek Vasut <marek.vasut@gmail.com>
Cc: Lukasz Majewski <l.majewski@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>
diff --git a/include/g_dnl.h b/include/g_dnl.h
index f47395f..f8affd8 100644
--- a/include/g_dnl.h
+++ b/include/g_dnl.h
@@ -23,7 +23,7 @@
 
 #include <linux/usb/ch9.h>
 #include <linux/usb/gadget.h>
-
+int g_dnl_bind_fixup(struct usb_device_descriptor *);
 int g_dnl_register(const char *s);
 void g_dnl_unregister(void);