Add python script to show hypervisor call statistics. Ex,

  # perf record -a -e "{powerpc:hcall_entry,powerpc:hcall_exit}"
  # perf script -s scripts/python/powerpc-hcalls.py
    hcall                            count   min(ns)   max(ns)   avg(ns)
    --------------------------------------------------------------------
    H_RANDOM                            82       838      1164       904
    H_PUT_TCE                           47      1078      5928      2003
    H_EOI                              266      1336      3546      1654
    H_ENTER                             28      1646      4038      1952
    H_PUT_TCE_INDIRECT                 230      2166     18168      6109
    H_IPI                              238      1072      3232      1688
    H_SEND_LOGICAL_LAN                  42      5488     21366      7694
    H_STUFF_TCE                        294       986      6210      3591
    H_XIRR                             266      2286      6990      3783
    H_PROTECT                           10      2196      3556      2555
    H_VIO_SIGNAL                       294      1028      2784      1311
    H_ADD_LOGICAL_LAN_BUFFER            53      1978      3450      2600
    H_SEND_CRQ                          77      1762      7240      2447
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20180605124801.17210-1-ravi.bangoria@linux.ibm.com
[ Fixup typo: table_loockup -> table_lookup ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>