kernel/scheduler: Skip setting invoke_scheduler in scheduler_reschedule_ici.

It isn't needed now that it's set before sending the ICI. Saves
a lot (hundreds, in some basic testing of compile jobs) of
unnecessary scheduler invocations.

src/system/kernel/scheduler/scheduler.cpp

@@ -223,8 +223,8 @@ void
 scheduler_reschedule_ici()
 {
 	// This function is called as a result of an incoming ICI.
-	// Make sure the reschedule() is invoked.
-	get_cpu_struct()->invoke_scheduler = true;
+	// Since invoke_scheduler will have been set by whatever sent the ICI, we
+	// shouldn't set it here (as the scheduler may have already cleared it.)
 }