pdbg: increase max chips to 32
pdbg: increase max chips to 32

POWER10 processors contain 32 addressable cores ("chips").

Signed-off-by: Nicholas Piggin <24829078df5003d9dd1dd871ca2aeb0b1cf95ef4@gmail.com>

open-power/pdbg,open-power/pdbg,open-power/pdbg