kernel: Reenable stack tracing in kernel-mode exceptions

Stack tracing in user-mode exceptions was moved to when a signal kills the process, but this isn't done for kernel-mode exceptions so there was no stack trace anymore.

kernel/src/arch/x86_64/CPU.cpp

@@ -105,6 +105,8 @@ void handle_cpu_exception(int signo, const char* err, Registers* regs)
         return;
     }
 
+    CPU::print_stack_trace_at(regs);
+
     CPU::efficient_halt();
 }