usb: gadget: midi: free hs descriptors

The HS descriptors are only created if HS is supported by the UDC but we
never free them.

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/f_midi.c

@@ -415,6 +415,7 @@ static void f_midi_unbind(struct usb_configuration *c, struct usb_function *f)
 	midi->id = NULL;
 
 	usb_free_descriptors(f->descriptors);
+	usb_free_descriptors(f->hs_descriptors);
 	kfree(midi);
 }