Kernel: Add and remove explicit keyword where needed

Author: https://github.com/supercomputer7
Commit: a431108ab6
Pull-request: https://github.com/SerenityOS/serenity/pull/3322
Issue: https://github.com/SerenityOS/serenity/issues/2393

Kernel/Interrupts/IRQHandler.h

@@ -57,7 +57,7 @@ public:
 
 protected:
     void change_irq_number(u8 irq);
-    IRQHandler(u8 irq);
+    explicit IRQHandler(u8 irq);
 
 private:
     bool m_shared_with_others { false };