pci: Display PCI IRQ pin in "info pci"

Sometimes it would be good to be able to read the pin number along
with the IRQ number allocated.  Since we'll dump the IRQ number, no
reason to not dump the pin information.  For example, the vfio-pci
device will overwrite the pin with the hardware pin number.  It would
be nice to know the pin number of one assigned device from QMP/HMP.

CC: Dr. David Alan Gilbert <dgilbert@redhat.com>
CC: Alex Williamson <alex.williamson@redhat.com>
CC: Michael S. Tsirkin <mst@redhat.com>
CC: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
CC: Julia Suvorova <jusual@redhat.com>
CC: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20200317195908.283800-1-peterx@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>