[MIPS] IP22: Fix detection of second HPC3 on Challenge S

The second HPC3 could be found only on Guiness systems (Challenge-S),
but not on fullhouse (Indigo2) systems.

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>