Section 3 "unauthorised modification of computer material" being the relevant element. There isn't, I think, an existing case which exactly mirrors this, but it is similar to the matter of "time locks" in software (where a program disabled itself after a given time). For a long time after the passage of the act, lawyers theorised that such locks might be illegal in some circumstances; the prosecution of Alfred Whittaker in Scunthorpe Magistrates Court in 1993 showed that it could be. But crucially in Whittaker, the locks were unknown to the customer (the company on whose computer the software was installed) - I don't think anyone thinks that time-limited trialware ("this software will stop working in 28 days unless activated") is illegal.
So whether FDTI are in trouble will depend on what expectation someone might have when installing the new driver (where the court assumes they actually read the licence screed). If the expectation was solely that it would improve their system or do nothing, they weren't giving consent, and FDTI may be found to have breached section 3. If the licence unambiguously said "this update will detect and disable fake or work-alike products without further interaction", they're probably fine. Likely the wording is much less clear, which is what keeps lawyers in jobs.
If all the bricked chips are counterfeits (that is, they have fake FDTI markings and have been passed of as real FDTI products), the Fiscal is probably going to say that a prosecution isn't in the public interest. The authorities, often working with trademark owners, have routinely seized counterfeit goods from unknowing individuals, with no compensation; they may argue this is an analogous case (sweeping analogies is what keeps judges in jobs). But if someone has been making FDTI workalike clones that aren't pretending (to consumers) that they're the FDTI product, their customers would have a better chance of twisting the Fiscal's arm.