perf tools: Rename perf_evlist__purge() to evlist__purge()

perf tools: Rename perf_evlist__purge() to evlist__purge()

Rename (perf_evlist__purge) to evlist__purge(), so we don't have a
name clash when we add (perf_evlist__purge) in libperf.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lore.kernel.org/lkml/20190913132355.21634-9-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>