parisc: Add constants for various PDC firmware calls

PDC_DEBUG, PDC_ALLOC and PDC_SCSI_PARMS were missing.
Add PDC_MODEL_GET_INSTALL_KERNEL and PDC_NVOLATILE_* subfunctions.
PDC_CONFIG is call #17, not 16. Luckily it's nowhere referenced yet.

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