perf top: Don't process samples with no valid machine object

perf top: Don't process samples with no valid machine object

The perf sample processing code relies on a valid machine object. Make
sure that this path is only entered when such a object exists.

A counter for samples where no machine object exits is also introduced
to give the user a message about these samples.

Reported-by: David Ahern <[email protected]>
Reported-by: Jason Wang <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jason Wang <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Joerg Roedel <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>