Platform/Sgi: ACPI CPPC support for RD-V1

Enable ACPI CPPC mechanism for RD-V1. The implementation uses AMU
registers accessible as Fixed-feature Hardware (FFixedHW) for monitoring
the performance. Non-secure SCMI fastchannels are used to communicate
with SCP to set the desired performance.

Change-Id: I96dcdf71c1e73b9f576250c1280a07621680caeb
Signed-off-by: Pranav Madhu <pranav.madhu@arm.com>