USB: Storage: Update unusual_devs entry for Datafab KECF-USB

This device suffers from the off-by-one error when reporting the capacity,
so add US_FL_FIX_CAPACITY to the existing entry.

Signed-off-by: Nick Holloway <Nick.Holloway@pyrites.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>