KVM: arm64: Hoist PMUv3 check into KVM_ARM_VCPU_INIT ioctl handler

Test that the system supports PMUv3 before ever getting to
kvm_reset_vcpu().

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Link: https://lore.kernel.org/r/20230920195036.1169791-3-oliver.upton@linux.dev


Signed-off-by: Oliver Upton <oliver.upton@linux.dev>