parisc: PDT/firmware: Add support to read PDT on older PAT-machines

Older machines with a PAT firmware (e.g. the rp5470) return their Page
Deallocation Table (PDT) info per cell via the PDC_PAT_MEM_PD_INFO PDC call.
This patch adds the necessary structures and wrappers to call firmware.

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