The interface for SiFive's PLIC was adopted and clarified by RISC-V as
the standard PLIC interface. Now that several PLIC implementations by
different vendors share this same interface, it is somewhat misleading
to report "SiFive PLIC" to userspace, when no SiFive hardware may be
present. This is especially the case when some implementations are
subtly incompatible with the binding and behavior of the SiFive PLIC,
yet are similar enough to share a driver.