Kernel: Fix GenericInterruptHandler problems with virtual functions

Because registering and unregistering interrupt handlers triggers
calls to virtual functions, we can't do this in the constructor
and destructor.

Fixes #5539

Kernel/Interrupts/IRQHandler.cpp

@@ -56,6 +56,8 @@ bool IRQHandler::eoi()
 void IRQHandler::enable_irq()
 {
     dbgln_if(IRQ_DEBUG, "Enable IRQ {}", interrupt_number());
+    if (!is_registered())
+        register_interrupt_handler();
     m_enabled = true;
     if (!m_shared_with_others)
         m_responsible_irq_controller->enable(*this);