usb: gadget: f_uac1: Add suspend callback

Add suspend callback to f_uac1 function, calling corresponding method
of u_audio in order to stop the respective PCM streams and to notify
subscribed clients about the stop.

Signed-off-by: Pavel Hofman <pavel.hofman@ivitera.com>
Link: https://lore.kernel.org/r/20220121155308.48794-11-pavel.hofman@ivitera.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>