This patch adds the implementation of the CFPC pSeries feature,
using the QEMU_CAPS_MACHINE_PSERIES_CAP_CFPC capability added
in the previous patch.

CPFC can have the values "broken", "workaround" or "fixed". Extra
code is required to handle it since it's not a regular tristate
capability.

This is the XML format for the cap:

<features>
  <cfpc value='workaround'/>
</features>
Signed-off-by: NDaniel Henrique Barboza <danielhb413@gmail.com>
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>