sbp2: make TSB42AA9 workaround specific to Momobay CX-1

The workarounds are not required for DViCO Momobay FX-3A and AFAIR not
for Momobay CX-2. These contain an TSB42AA9A but feature the same
firmware_revision value as the older DViCO Momobay CX-1.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Ben Collins <bcollins@ubuntu.com>