usb: f_uac2: adds support for SS and SSP

Patch adds support of SS and SSP speed.

Signed-off-by: Pawel Laszczak <pawell@cadence.com>
Link: https://lore.kernel.org/r/20210310105216.38202-1-pawell@gli-login.cadence.com


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