Move PSCI triage to C

There's no reason we need to test the PSCI function IDs in assembly;
move this to C so that it can be shared across AArch64 and AArch32. At
the same time, limit the PSCI_CPU_ON FIDs to match the register width of
the kernel.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
3 files changed