bebob: add changing sampling frequency support for Focusrite devices

Accodrding to FFADO, to changing sampling rate, Saffire and Saffile LE
use Input/Output Plug Signal Format command but SaffirePro series use its own
register. And there are two registers to change sampling frequency. One
accompanies bus reset and another don't.

This commit support without bus reset.
bebob: supplement Kconfig