ppc/pnv: Fix OCC common area region mapping

ppc/pnv: Fix OCC common area region mapping

The OCC common area is mapped at a unique address on the system and
each OCC is assigned a segment to expose its sensor data :

  -------------------------------------------------------------------------
  | Start (Offset from | End           | Size     |Description            |
  | BAR2 base address) |               |          |                       |
  -------------------------------------------------------------------------
  |    0x00580000      |  0x005A57FF   |150kB     |OCC 0 Sensor Data Block|
  |    0x005A5800      |  0x005CAFFF   |150kB     |OCC 1 Sensor Data Block|
  |        :           |       :       |  :       |            :          |
  |    0x00686800      |  0x006ABFFF   |150kB     |OCC 7 Sensor Data Block|
  |    0x006AC000      |  0x006FFFFF   |336kB     |Reserved               |
  -------------------------------------------------------------------------

Maximum size is 1.5MB.

We could define a "OCC common area" memory region at the machine level
and sub regions for each OCC. But it adds some extra complexity to the
models. Fix the current layout with a simpler model.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20191211082912.2625-3-clg@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>