perf intel-pt: Add lookahead callback

perf intel-pt: Add lookahead callback

Add a callback function to enable the decoder to lookahead at subsequent
trace buffers. This will be used to implement a "fast forward" facility
which will be needed to support efficient time interval filtering.

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/20190604130017.31207-5-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>