arm64: pmuv3: use arm_pmu ACPI framework

Now that we have a framework to handle the ACPI bits, make the PMUv3
code use this. The framework is a little different to what was
originally envisaged, and we can drop some unused support code in the
process of moving over to it.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Jeremy Linton <jeremy.linton@arm.com>
[will: make armv8_pmu_driver_init static]
Signed-off-by: Will Deacon <will.deacon@arm.com>