Kernel: Use a const reference to RegisterState in IRQ handling

Author: https://github.com/supercomputer7
Commit: e880fe0765
Pull-request: https://github.com/SerenityOS/serenity/pull/1396
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/shannonbooth ✅

Kernel/Net/RTL8139NetworkAdapter.cpp

@@ -177,7 +177,7 @@ RTL8139NetworkAdapter::~RTL8139NetworkAdapter()
 {
 }
 
-void RTL8139NetworkAdapter::handle_irq(RegisterState&)
+void RTL8139NetworkAdapter::handle_irq(const RegisterState&)
 {
     for (;;) {
         int status = in16(REG_ISR);