perf machine: Factor machine__find_thread to take tid argument

perf machine: Factor machine__find_thread to take tid argument

Forcing the code to always search thread by pid/tid pair.

The PID value will be needed in future to determine the process thread
leader for map groups sharing.

Signed-off-by: Jiri Olsa <[email protected]>
Acked-by: Adrian Hunter <[email protected]>
Cc: Corey Ashford <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Don Zickus <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>