perf smt: Tidy header guard add SPDX

Make the header guard consistent with others.
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Caleb Biggers <caleb.biggers@intel.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.garry@huawei.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Kshipra Bopardikar <kshipra.bopardikar@intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Miaoqian Lin <linmq006@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Perry Taylor <perry.taylor@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Cc: florian fischer <florian.fischer@muhq.space>
Link: http://lore.kernel.org/lkml/20220830164846.401143-2-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/smt.c

+// SPDX-License-Identifier: GPL-2.0-only
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>

tools/perf/util/smt.h

-#ifndef SMT_H
-#define SMT_H 1
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __SMT_H
+#define __SMT_H 1
 
 int smt_on(void);
 
-#endif
+#endif /* __SMT_H */