Fix the LED mode handling

First of all, to disallow switching to LEDNumlock, we need to do the check in
the `.init()` method, not in `.setup()`. Second, tracking the previous LED mode
can be done a lot simpler - and a lot reliably.

With these changes, the NumLock LED effect works as it is expected to.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>

src/Keyboardio-LEDEffect-Numlock.cpp

@@ -18,7 +18,7 @@ LEDNumlock::begin (void) {
 }
 
 void
-LEDNumlock::setup (void) {
+LEDNumlock::init (void) {
     if (!Layer.isOn (numpadIndex)) {
         LEDControl.next_mode();
     }
@@ -42,15 +42,11 @@ LEDNumlock::loopHook (bool postClear) {
     if (!postClear)
         return;
 
-    if (Layer.isOn (numpadIndex)) {
-        if (storedLEDMode != us) {
+    if (!Layer.isOn (numpadIndex)) {
+        if (LEDControl.get_mode () != us)
             storedLEDMode = LEDControl.get_mode ();
-        }
-        LEDControl.set_mode (us);
-    }
-
-    if (!Layer.isOn (numpadIndex) &&
-            LEDControl.get_mode () == us) {
         LEDControl.set_mode (storedLEDMode);
+    } else {
+        LEDControl.set_mode (us);
     }
 }

src/Keyboardio-LEDEffect-Numlock.h

@@ -10,7 +10,7 @@ class LEDNumlock : LEDMode {
   virtual void begin (void) final;
 
   virtual void update (void) final;
-  virtual void setup (void) final;
+  virtual void init (void) final;
 
  private:
   static void loopHook (bool postClear);