usb: gadget: midi: f_midi_alloc() can be static

drivers/usb/gadget/function/f_midi.c:1072:21: sparse: symbol 'f_midi_alloc' was not declared. Should it be static?
drivers/usb/gadget/legacy/gmidi.c:118:30: sparse: symbol 'fi_midi' was not declared. Should it be static?
drivers/usb/gadget/legacy/gmidi.c:119:21: sparse: symbol 'f_midi' was not declared. Should it be static?

Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/function/f_midi.c

@@ -1097,7 +1097,7 @@ static void f_midi_unbind(struct usb_configuration *c, struct usb_function *f)
 	usb_free_all_descriptors(f);
 }
 
-struct usb_function *f_midi_alloc(struct usb_function_instance *fi)
+static struct usb_function *f_midi_alloc(struct usb_function_instance *fi)
 {
 	struct f_midi *midi;
 	struct f_midi_opts *opts;

drivers/usb/gadget/legacy/gmidi.c

@@ -115,8 +115,8 @@ static struct usb_gadget_strings *dev_strings[] = {
 	NULL,
 };
 
-struct usb_function_instance *fi_midi;
-struct usb_function *f_midi;
+static struct usb_function_instance *fi_midi;
+static struct usb_function *f_midi;
 
 static int __exit midi_unbind(struct usb_composite_dev *dev)
 {