perf intel-pt: Add support for lookahead

perf intel-pt: Add support for lookahead

Implement the lookahead callback to let the decoder access subsequent
buffers. intel_pt_lookahead() manages the buffer lifetime and calls the
decoder for each buffer until the decoder returns a non-zero value.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20190604130017.31207-11-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>