MFC r346489:

Move the reporting of spurious interrupts under bootverbose control, because
occasional spurious interrupts are a normal thing on this hardware. Also,
change the name of the cpu-local interrupt controller driver from local_intc
to lintc, because the name gets built into interrupt names, which have to
fit into a 19-byte field for stats reporting (so this allows 5 more bytes
of the actual interrupt name to be displayed).