ppc/pnv: Add models for POWER9 PHB4 PCIe Host bridge

These changes introduces models for the PCIe Host Bridge (PHB4) of the
POWER9 processor. It includes the PowerBus logic interface (PBCQ),
IOMMU support, a single PCIe Gen.4 Root Complex, and support for MSI
and LSI interrupt sources as found on a POWER9 system using the XIVE
interrupt controller.

POWER9 processor comes with 3 PHB4 PEC (PCI Express Controller) and
each PEC can have several PHBs. By default,

  * PEC0 provides 1 PHB  (PHB0)
  * PEC1 provides 2 PHBs (PHB1 and PHB2)
  * PEC2 provides 3 PHBs (PHB3, PHB4 and PHB5)

Each PEC has a set  "global" registers and some "per-stack" (per-PHB)
registers. Those are organized in two XSCOM ranges, the "Nest" range
and the "PCI" range, each range contains both some "PEC" registers and
some "per-stack" registers.

No default device layout is provided and PCI devices can be added on
any of the available PCIe Root Port (pcie.0 .. 2 of a Power9 chip)
with address 0x0 as the firwware (skiboot) only accepts a single
device per root port. To run a simple system with a network and a
storage adapters, use a command line options such as :

  -device e1000e,netdev=net0,mac=C0:FF:EE:00:00:02,bus=pcie.0,addr=0x0
  -netdev bridge,id=net0,helper=/usr/libexec/qemu-bridge-helper,br=virbr0,id=hostnet0

  -device megasas,id=scsi0,bus=pcie.1,addr=0x0
  -drive file=$disk,if=none,id=drive-scsi0-0-0-0,format=qcow2,cache=none
  -device scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0,bootindex=2

If more are needed, include a bridge.

Multi chip is supported, each chip adding its set of PHB4 controllers
and its PCI busses. The model doesn't emulate the EEH error handling.

This model is not ready for hotplug yet.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
[ clg: - numerous cleanups
       - commit log
       - fix for broken LSI support
       - PHB pic printinfo
       - large QOM rework ]
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20200127144506.11132-2-clg@kaod.org>
[dwg: Use device_class_set_props()]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>