ppc/p4080: Add support for CoreNet style platform LAWs

On CoreNet based platforms the LAW address is split between an high &
low register and we no longer shift the address.  Also, the target IDs
on CoreNet platforms have been completely re-assigned.

Additionally, added a new find_law() API to which LAW an address hits in.
This is need for the CoreNet style boot release code since it will need
to determine what the target ID should be set to for boot window
translation.

Finally, enamed LAWAR_EN to LAW_EN and moved to header so we can use
it elsewhere.

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