powerpc/mpc85xx: Fix core cluster PLL calculation for Chassis generation 2

powerpc/mpc85xx: Fix core cluster PLL calculation for Chassis generation 2

Corenet based SoCs have different core clocks starting from Chassis
generation 2. Cores are organized into clusters. Each cluster has up to
4 cores sharing same clock, which can be chosen from one of three PLLs in
the cluster group with one of the devisors /1, /2 or /4. Two clusters are
put together as a cluster group. These two clusters share the PLLs but may
have different divisor. For example, core 0~3 are in cluster 1. Core 4~7
are in cluster 2. Core 8~11 are in cluster 3 and so on. Cluster 1 and 2
are cluster group A. Cluster 3 and 4 are in cluster group B. Cluster group
A has PLL1, PLL2, PLL3. Cluster group B has PLL4, PLL5. Core 0~3 may have
PLL1/2, core 4~7 may have PLL2/2. Core 8~11 may have PLL4/1.

PME and FMan blocks can take different PLLs, configured by RCW.

Signed-off-by: York Sun <yorksun@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>