Limit Case Light PWM (#15459)

Marlin/src/inc/Conditionals_post.h

@@ -1334,6 +1334,17 @@
   #define FAST_PWM_FAN_FREQUENCY ((F_CPU) / (2 * 255 * 1)) // Fan frequency default
 #endif
 
+/**
+ * MIN/MAX case light PWM scaling
+ */
+#if HAS_CASE_LIGHT
+  #ifndef CASE_LIGHT_MAX_PWM
+    #define CASE_LIGHT_MAX_PWM 255
+  #elif !WITHIN(CASE_LIGHT_MAX_PWM, 1, 255)
+    #error "CASE_LIGHT_MAX_PWM must be a value from 1 to 255."
+  #endif
+#endif
+
 /**
  * Bed Probe dependencies
  */