usb: gadget: f_uac1: Staticize local functions

control_selector_init() is used only in this file.
audio_bind_config() is used only in audio.c file to which
f_uac1.c is included. Thus, these functions are staticized
to fix the following warnings.

drivers/usb/gadget/f_uac1.c:698:12: warning: symbol 'control_selector_init' was not declared. Should it be static?
drivers/usb/gadget/f_uac1.c:722:12: warning: symbol 'audio_bind_config' was not declared. Should it be static?

Acked-by: Jassi Brar <[e-mail]>
Signed-off-by: Jingoo Han <[e-mail]>
Signed-off-by: Felipe Balbi <[e-mail]>

drivers/usb/gadget/f_uac1.c

···
 }
 
 /* Todo: add more control selecotor dynamically */
-int __init control_selector_init(struct f_audio *audio)
+static int __init control_selector_init(struct f_audio *audio)
 {
 	INIT_LIST_HEAD(&audio->cs);
 	list_add(&feature_unit.list, &audio->cs);
···
  *
  * Returns zero on success, else negative errno.
  */
-int __init audio_bind_config(struct usb_configuration *c)
+static int __init audio_bind_config(struct usb_configuration *c)
 {
 	struct f_audio *audio;
 	int status;