perf mmap: Simplify perf_mmap__read_init()

It isn't necessary to pass the 'start', 'end' and 'overwrite' arguments
to perf_mmap__read_init().  The data is stored in the struct perf_mmap.

Discard the parameters.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Suggested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1520350567-80082-8-git-send-email-kan.liang@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/tests/task-exit.c b/tools/perf/tests/task-exit.c
index 2df0c05..e92fa60 100644
--- a/tools/perf/tests/task-exit.c
+++ b/tools/perf/tests/task-exit.c
@@ -48,7 +48,6 @@ int test__task_exit(struct test *test __maybe_unused, int subtest __maybe_unused
 	struct cpu_map *cpus;
 	struct thread_map *threads;
 	struct perf_mmap *md;
-	u64 end, start;
 
 	signal(SIGCHLD, sig_handler);
 
@@ -113,7 +112,7 @@ int test__task_exit(struct test *test __maybe_unused, int subtest __maybe_unused
 
 retry:
 	md = &evlist->mmap[0];
-	if (perf_mmap__read_init(md, false, &start, &end) < 0)
+	if (perf_mmap__read_init(md) < 0)
 		goto out_init;
 
 	while ((event = perf_mmap__read_event(md)) != NULL) {