Define arch_init_invariance_cppc() to use highest performance values
from _CPC objects to obtain and set maximum capacity information for
each CPU.

The performance scale used by CPPC is a unified scale for all CPUs in
the system. Therefore, by obtaining the raw highest performance values
from the _CPC objects, and normalizing them on the [0, 1024] capacity
scale used by the task scheduler we obtain the CPU capacity of each
CPU.

Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>