config: Add missing CPUs to --restore-with-cpu

The --restore-with-cpu option didn't use CpuConfig.cpu_names() to
determine which CPU names are valid, instead it used a static list of
known CPU names. This changeset makes the option parsing code use the
CPU list from the CpuConfig module instead.
kvm: Add support for disabling coalesced MMIO

Add the option useCoalescedMMIO to the BaseKvmCPU. The default
behavior is to disable coalesced MMIO since this hasn't been heavily
tested.