perf tools: Use __maybe_unused consistently

Instead of defining __unused or redefining __maybe_unused.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-4eleto5pih31jw1q4dypm9pf@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/bench/numa.c

@@ -700,7 +700,7 @@ static inline uint32_t lfsr_32(uint32_t lfsr)
  * kernel (KSM, zero page, etc.) cannot optimize away RAM
  * accesses:
  */
-static inline u64 access_data(u64 *data __attribute__((unused)), u64 val)
+static inline u64 access_data(u64 *data, u64 val)
 {
 	if (g->p.data_reads)
 		val += *data;