perf mmap: Cleanup perf_mmap__push()

The first assignment for 'start' and 'end' is redundant.
Signed-off-by: Kan Liang <kan.liang@intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1516310792-208685-4-git-send-email-kan.liang@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/mmap.c

@@ -272,7 +272,7 @@ int perf_mmap__push(struct perf_mmap *md, bool overwrite,
 {
 	u64 head = perf_mmap__read_head(md);
 	u64 old = md->prev;
-	u64 end = head, start = old;
+	u64 end, start;
 	unsigned char *data = md->base + page_size;
 	unsigned long size;
 	void *buf;