usb: gadget: f_uac1: stop playback on function disable

There is missing playback stop/cleanup in case of
gadget's ->disable callback that happens on
events like USB host resetting or gadget disconnection

Fixes: 0591bc23 ("usb: gadget: add f_uac1 variant based on a new u_audio api")
Cc: <stable@vger.kernel.org> # 4.13+
Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
Link: https://lore.kernel.org/r/1614599375-8803-3-git-send-email-ruslan.bilovol@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/function/f_uac1.c

@@ -499,6 +499,7 @@ static void f_audio_disable(struct usb_function *f)
 	uac1->as_out_alt = 0;
 	uac1->as_in_alt = 0;
 
+	u_audio_stop_playback(&uac1->g_audio);
 	u_audio_stop_capture(&uac1->g_audio);
 }