g_dnl: add missing declaration

Signed-off-by: Steve Rae <srae@broadcom.com>
Tested-by: Lukasz Majewski <l.majewski@samsung.com>
Test HW: Exynos 4210 (trats), Exynos 5422 (Odroid XU3)

include/g_dnl.h

@@ -34,6 +34,7 @@ struct g_dnl_bind_callback {
 };
 
 int g_dnl_bind_fixup(struct usb_device_descriptor *, const char *);
+int g_dnl_get_board_bcd_device_number(int gcnum);
 int g_dnl_board_usb_cable_connected(void);
 int g_dnl_register(const char *s);
 void g_dnl_unregister(void);