Sanity check that auto fan pins can do PWM

Marlin/SanityCheck.h

@@ -871,6 +871,23 @@
 #endif
 
 /**
+ * Auto Fan check for PWM pins
+ */
+#if HAS_AUTO_FAN && EXTRUDER_AUTO_FAN_SPEED != 255
+  #define AF_ERR_SUFF "_AUTO_FAN_PIN is not a PWM pin. Set EXTRUDER_AUTO_FAN_SPEED to 255."
+  #if HAS_AUTO_FAN_0
+    static_assert(GET_TIMER(E0_AUTO_FAN_PIN), "E0" AF_ERR_SUFF);
+  #elif HAS_AUTO_FAN_1
+    static_assert(GET_TIMER(E1_AUTO_FAN_PIN), "E1" AF_ERR_SUFF);
+  #elif HAS_AUTO_FAN_2
+    static_assert(GET_TIMER(E2_AUTO_FAN_PIN), "E2" AF_ERR_SUFF);
+  #elif HAS_AUTO_FAN_3
+    static_assert(GET_TIMER(E3_AUTO_FAN_PIN), "E3" AF_ERR_SUFF);
+  #endif
+#endif
+
+
+/**
  * Make sure only one display is enabled
  *
  * Note: BQ_LCD_SMART_CONTROLLER => REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER