Disable spreadcycle in tmc_enable_stallguard<2209> (#16890)

Marlin/src/feature/tmc_util.cpp

@@ -1096,8 +1096,11 @@
   }
 
   bool tmc_enable_stallguard(TMC2209Stepper &st) {
+    const bool stealthchop_was_enabled = !st.en_spreadCycle();
+    
     st.TCOOLTHRS(0xFFFFF);
-    return !st.en_spreadCycle();
+    st.en_spreadCycle(false);
+    return stealthchop_was_enabled;
   }
   void tmc_disable_stallguard(TMC2209Stepper &st, const bool restore_stealth) {
     st.en_spreadCycle(!restore_stealth);