perf top: Drop samples which are behind the refresh rate

Drop samples from processing thread if they get behind the latest event
read from the kernel maps. If it gets behind more than the refresh rate
(-d option), drop the sample.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/n/tip-x533ra5c1pgofvbtsizzuydd@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>