ppc/pnv: introduce a new pic_print_info() operation to the chip model

The POWER9 and POWER8 processors have different interrupt controllers,
and reporting their state requires calling different helper routines.

However, the interrupt presenters are still handled in the higher
level pic_print_info() routine because they are not related to the
chip.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20190306085032.15744-9-clg@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>