product/rdn2: add CPU PIK register space declaration

CPU PIK includes registers for configuration and clock control for AP
cores. Add the register space declaration and the base address macro for
the CPU PIK.

Change-Id: I5b0e76d310579563af5c2b536d3323c4c1c1d24c
Signed-off-by: Aditya Angadi <aditya.angadi@arm.com>