Disallow PMU events intel_pt and intel_bts until the tools support them.

By default any PMU is selectable as an event but until the tools have
intel_pt and intel_bts support using them would result in no data being
recorded without any indication as to why.

Before the change:

    $ perf record -e intel_bts// sleep 1
    [ perf record: Woken up 1 times to write data ]
    [ perf record: Captured and wrote 0.008 MB perf.data ]
    $ perf report --stdio
    Error:
    The perf.data file has no samples!

After the change:

    $ perf record -e intel_bts// sleep 1
    invalid or unsupported event: 'intel_bts//'
    Run 'perf list' for a list of valid events
Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1432295653-13989-2-git-send-email-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>