ksys/util: Add Event::isSignalSet

Missed it because of IDA's function tail mechanism...

src/KingSystem/Utils/Thread/Event.cpp

@@ -47,4 +47,8 @@ void Event::resetSignal() {
     mSignalSet.exchange(0);
 }
 
+bool Event::isSignalSet() const {
+    return mSignalSet == 1;
+}
+
 }  // namespace ksys::util

src/KingSystem/Utils/Thread/Event.h

@@ -22,6 +22,8 @@ public:
     void setSignal();
     void resetSignal();
 
+    bool isSignalSet() const;
+
 private:
     bool mManualReset = false;
     sead::Atomic<u32> mSignalSet = 0;