powerpc/mpc85xx: Add revision properties in portal device tree node 'pme'

powerpc/mpc85xx: Add revision properties in portal device tree node 'pme'

The 'fsl,pme-rev1' and 'fsl-pme-rev2' properties have been added to the
pme portal node. This is required for software to determine which version
of PME hardware is present and take appropriate actions.
These properties are a direct reflection of the corresponding ccsr pme
register value.

Also removed unnecessary static global variables.

Signed-off-by: Jeffrey Ladouceur <Jeffrey.Ladouceur@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>