Use standard timeout checker for LEDEffect-Rainbow

Also, change `rainbow_update_delay` from two bytes to one, and use a more
consistent interval by adding it to `rainbow_last_update` after each update,
rather than using the current time.

Signed-off-by: Michael Richters <gedankenexperimenter@gmail.com>

src/kaleidoscope/plugin/LEDEffect-Rainbow.cpp

@@ -23,11 +23,11 @@ void LEDRainbowEffect::TransientLEDMode::update(void) {
   if (!Kaleidoscope.has_leds)
     return;
 
-  uint16_t now = millis();
-  if ((now - rainbow_last_update) < parent_->rainbow_update_delay) {
+  if (!Kaleidoscope.hasTimeExpired(rainbow_last_update,
+                                   parent_->rainbow_update_delay)) {
     return;
   } else {
-    rainbow_last_update = now;
+    rainbow_last_update += parent_->rainbow_update_delay;
   }
 
   cRGB rainbow = hsvToRgb(rainbow_hue, rainbow_saturation, parent_->rainbow_value);
@@ -54,11 +54,11 @@ void LEDRainbowWaveEffect::TransientLEDMode::update(void) {
   if (!Kaleidoscope.has_leds)
     return;
 
-  uint16_t now = millis();
-  if ((now - rainbow_last_update) < parent_->rainbow_update_delay) {
+  if (!Kaleidoscope.hasTimeExpired(rainbow_last_update,
+                                   parent_->rainbow_update_delay)) {
     return;
   } else {
-    rainbow_last_update = now;
+    rainbow_last_update += parent_->rainbow_update_delay;
   }
 
   for (int8_t i = 0; i < LED_COUNT; i++) {

src/kaleidoscope/plugin/LEDEffect-Rainbow.h

@@ -55,13 +55,13 @@ class LEDRainbowEffect : public Plugin,
     uint16_t rainbow_hue = 0;   //  stores 0 to 614
 
     uint8_t rainbow_steps = 1;  //  number of hues we skip in a 360 range per update
-    uint16_t rainbow_last_update = 0;
+    uint8_t rainbow_last_update = 0;
 
     byte rainbow_saturation = 255;
   };
 
  private:
-  uint16_t rainbow_update_delay = 40; // delay between updates (ms)
+  uint8_t rainbow_update_delay = 40; // delay between updates (ms)
   byte rainbow_value = 50;
 };
 
@@ -100,12 +100,12 @@ class LEDRainbowWaveEffect : public Plugin, public LEDModeInterface {
     uint16_t rainbow_hue = 0;  //  stores 0 to 614
 
     uint8_t rainbow_wave_steps = 1;  //  number of hues we skip in a 360 range per update
-    uint16_t rainbow_last_update = 0;
+    uint8_t rainbow_last_update = 0;
 
     byte rainbow_saturation = 255;
   };
 
-  uint16_t rainbow_update_delay = 40; // delay between updates (ms)
+  uint8_t rainbow_update_delay = 40; // delay between updates (ms)
   byte rainbow_value = 50;
 };
 }