usb: gadget: u_audio: clean up some inconsistent indenting

Eliminate the follow smatch warning:

drivers/usb/gadget/function/u_audio.c:1182 g_audio_setup() warn:
inconsistent indenting.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220407062410.89214-1-jiapeng.chong@linux.alibaba.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>