Fix declaration order in util/system.h

Summary: This was fubared in D3953

Test Plan:
  make check

Reviewers: #bitcoin_abc, majcosta

Reviewed By: majcosta

Differential Revision: https://reviews.bitcoinabc.org/D5841

src/util/system.h

@@ -362,6 +362,15 @@ template <typename Callable> void TraceThread(const char *name, Callable func) {
 
 std::string CopyrightHolders(const std::string &strPrefix);
 
+/**
+ * On platforms that support it, tell the kernel the calling thread is
+ * CPU-intensive and non-interactive. See SCHED_BATCH in sched(7) for details.
+ *
+ * @return The return value of sched_setschedule(), or 1 on systems without
+ * sched_setchedule().
+ */
+int ScheduleBatchPriority();
+
 namespace util {
 
 //! Simplification of std insertion
@@ -390,13 +399,4 @@ class WinCmdLineArgs {
 
 } // namespace util
 
-/**
- * On platforms that support it, tell the kernel the calling thread is
- * CPU-intensive and non-interactive. See SCHED_BATCH in sched(7) for details.
- *
- * @return The return value of sched_setschedule(), or 1 on systems without
- * sched_setchedule().
- */
-int ScheduleBatchPriority();
-
 #endif // BITCOIN_UTIL_SYSTEM_H