Kernel: Fix always-true comparison warnings

Author: https://github.com/BertalanD
Commit: fda9f394d1
Pull-request: https://github.com/SerenityOS/serenity/pull/8354
Reviewed-by: https://github.com/Hendiadyoin1
Reviewed-by: https://github.com/alimpfard

Kernel/Scheduler.cpp

@@ -460,7 +460,7 @@ Process* Scheduler::colonel()
 
 UNMAP_AFTER_INIT void Scheduler::initialize()
 {
-    VERIFY(&Processor::current() != nullptr); // sanity check
+    VERIFY(Processor::is_initialized()); // sanity check
 
     RefPtr<Thread> idle_thread;
     g_finalizer_wait_queue = new WaitQueue;