usb: gadget: midi: avoid redundant f_midi_set_alt() call

Function midi registers two interfaces with single set_alt() function
which means that f_midi_set_alt() is called twice when configuration
is set. That means that endpoint initialization and ep request allocation
is done two times. To avoid this problem we do such things only once,
for interface number 1 (MIDI Streaming interface).
Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/function/f_midi.c

@@ -329,6 +329,10 @@ static int f_midi_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
 	unsigned i;
 	int err;
 
+	/* For Control Device interface we do nothing */
+	if (intf == 0)
+		return 0;
+
 	err = f_midi_start_ep(midi, f, midi->in_ep);
 	if (err)
 		return err;