ppc/p4080: Determine various chip frequencies on CoreNet platforms

The means to determine the core, bus, and DDR frequencies are completely
new on CoreNet style platforms.  Additionally on p4080 we can have
different frequencies for FMAN and PME IP blocks.  We need to keep track
of the FMAN & PME frequencies since they are used for time stamping
capabilities inside each block.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>