perf lock: Fix a copy-n-paste bug

It should be lock_text_end instead of _start.

Fixes: 0d2997f7 ("perf lock: Look up callchain for the contended locks")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20220721043644.153718-2-namhyung@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-lock.c

@@ -892,7 +892,7 @@ static bool is_lock_function(u64 addr)
 		sym = machine__find_kernel_symbol_by_name(machine,
 							  "__lock_text_end",
 							  &kmap);
-		lock_text_start = kmap->unmap_ip(kmap, sym->start);
+		lock_text_end = kmap->unmap_ip(kmap, sym->start);
 	}
 
 	/* failed to get kernel symbols */