target/ppc/spapr: Add H-Call H_GET_CPU_CHARACTERISTICS
    
    The new H-Call H_GET_CPU_CHARACTERISTICS is used by the guest to query
    behaviours and available characteristics of the cpu.
    
    Implement the handler for this new H-Call which formulates its response
    based on the setting of the spapr_caps cap-cfpc, cap-sbbc and cap-ibs.
    
    Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
    Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
    (cherry picked from commit c59704b254734182c3202e0c261589ea2ccf485e)
    Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>