usb: gadget: uac1: struct gaudio is useless for struct f_uac1_opts

Since we call gaudio_cleanup at f_audio_free, the f_uac1_opts
doesn't need to use gaudio any more.

Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>