parisc: Add PDCE_CHECK instruction to HPMC handler

According to the programming note at page 1-31 of the PA 1.1 Firmware
Architecture document, one should use the PDC_INSTR firmware function to
get the instruction that invokes a PDCE_CHECK in the HPMC handler.  This
patch follows this note and sets the instruction which has been a nop up
until now.
Testing on a C3000 and C8000 showed that this firmware call isn't
implemented on those machines, so maybe it's only needed on older ones.

Signed-off-by: Helge Deller <deller@gmx.de>