ppc/pnv: Connect I2C controller model to powernv9 chip

ppc/pnv: Connect I2C controller model to powernv9 chip

Wires up three I2C controller instances to the powernv9 chip
XSCOM address space.

Each controller instance is wired up to a single I2C bus of
its own.  No other I2C devices are connected to the buses
at this time.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
[milesg: Split wiring from addition of model itself]
[milesg: Added new commit message]
[milesg: Moved hardcoded attributes into PnvChipClass]
[milesg: Removed TODO comment for I2C]
Signed-off-by: Glenn Miles <milesg@linux.vnet.ibm.com>
Acked-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-ID: <20231016222013.3739530-3-milesg@linux.vnet.ibm.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>