tracing: Fix SPDX format headers to use C++ style comments

The Linux kernel adopted the SPDX License format headers to ease license
compliance management, and uses the C++ '//' style comments for the SPDX
header tags. Some files in the tracing directory used the C style /* */
comments for them. To be consistent across all files, replace the /* */
C style SPDX tags with the C++ // SPDX tags.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace.h

-/* SPDX-License-Identifier: GPL-2.0 */
+// SPDX-License-Identifier: GPL-2.0
 
 #ifndef _LINUX_KERNEL_TRACE_H
 #define _LINUX_KERNEL_TRACE_H

kernel/trace/trace_benchmark.h

-/* SPDX-License-Identifier: GPL-2.0 */
+// SPDX-License-Identifier: GPL-2.0
 #undef TRACE_SYSTEM
 #define TRACE_SYSTEM benchmark
 

kernel/trace/trace_entries.h

-/* SPDX-License-Identifier: GPL-2.0 */
+// SPDX-License-Identifier: GPL-2.0
 /*
  * This file defines the trace event structures that go into the ring
  * buffer directly. They are created via macros so that changes for them

kernel/trace/trace_events_filter_test.h

-/* SPDX-License-Identifier: GPL-2.0 */
+// SPDX-License-Identifier: GPL-2.0
 #undef TRACE_SYSTEM
 #define TRACE_SYSTEM test
 

kernel/trace/trace_kprobe_selftest.h

-/* SPDX-License-Identifier: GPL-2.0 */
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Function used during the kprobe self test. This function is in a separate
  * compile unit so it can be compile with CC_FLAGS_FTRACE to ensure that it

kernel/trace/trace_output.h

-/* SPDX-License-Identifier: GPL-2.0 */
+// SPDX-License-Identifier: GPL-2.0
 #ifndef __TRACE_EVENTS_H
 #define __TRACE_EVENTS_H
 

kernel/trace/trace_stat.h

-/* SPDX-License-Identifier: GPL-2.0 */
+// SPDX-License-Identifier: GPL-2.0
 #ifndef __TRACE_STAT_H
 #define __TRACE_STAT_H
 

kernel/trace/tracing_map.h

-/* SPDX-License-Identifier: GPL-2.0 */
+// SPDX-License-Identifier: GPL-2.0
 #ifndef __TRACING_MAP_H
 #define __TRACING_MAP_H