ppc: add a IBM 40p machine (RS/6000, PReP)

Hi,

This patchset adds the emulation of the IBM RS/6000 7020 (40p). The real machine is able to run AIX (up to 4.3.3), Windows NT (up to 4.0 SP1), the beta of OS/2 PowerPC, Solaris, Linux, NetBSD/PReP ...

I've tested current emulation with Open Hack'Ware, OpenBIOS and official firmware.

Linux kernel starts, and freezes during boot (seems like a problem with the SCSI adapter). Windows NT starts up to the point where it wants to change endianness. Other OSes have not been tested.

This machine is a superset of the 'prep' one, because we know exactly what is/should emulated, and that operating system list running on it is quite wide. I hope that 'prep' machine can be deprecated soon and then later removed.

Patch 1 is a cleanup, and can probably be committed first. Patches 2 to 4 are the real implementation of the IBM 40p.

Changes since v2:
- patch 2: fix mismatch between read and write functions for port 92
- patch 4: use error_report instead of fprintf/hw_error

Changes since v1:
- removed patches related to display adapter:
Let's wait for an emulation of the real display adapter (an S3 Trio), as current VGA adapter already mostly works with Open Hack'Ware and OpenBIOS
- various changes due to David Gibson's remarks

Hervé Poussineau (4):
prep: do not use global variable to access nvram
prep: add PReP System I/O
prep: add IBM RS/6000 7020 (40p) memory controller
prep: add IBM RS/6000 7020 (40p) machine emulation

 default-configs/ppc-softmmu.mak |   2 +
 hw/ppc/Makefile.objs            |   2 +
 hw/ppc/prep.c                   | 233 +++++++++++++++++++++++++++++-
 hw/ppc/prep_systemio.c          | 303 ++++++++++++++++++++++++++++++++++++++++
 hw/ppc/rs6000_mc.c              | 232 ++++++++++++++++++++++++++++++
 hw/ppc/trace-events             |  11 ++
 6 files changed, 781 insertions(+), 2 deletions(-)
 create mode 100644 hw/ppc/prep_systemio.c
 create mode 100644 hw/ppc/rs6000_mc.c

2.1.4