USB: Add more empty functions in otg.h

Add empty functions for get/put transceiver functions too, so that
drivers that optionally use them can call them without worrying that
they might not exist, eliminating ifdefs.

Signed-off-by: Grazvydas Ignotas <[e-mail]>
Acked-by: Felipe Balbi <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

include/linux/usb/otg.h

···
 }
 
 /* for usb host and peripheral controller drivers */
+#ifdef CONFIG_USB_OTG_UTILS
 extern struct otg_transceiver *otg_get_transceiver(void);
 extern void otg_put_transceiver(struct otg_transceiver *);
+#else
+static inline struct otg_transceiver *otg_get_transceiver(void)
+{
+	return NULL;
+}
+
+static inline void otg_put_transceiver(struct otg_transceiver *x)
+{
+}
+#endif
 
 /* Context: can sleep */
 static inline int