🐛 Fix MMU1 compile (#22965)

Marlin/src/MarlinCore.cpp

@@ -216,6 +216,10 @@
   #include "feature/controllerfan.h"
 #endif
 
+#if HAS_PRUSA_MMU1
+  #include "feature/mmu/mmu.h"
+#endif
+
 #if HAS_PRUSA_MMU2
   #include "feature/mmu/mmu2.h"
 #endif

Marlin/src/feature/mmu/mmu.cpp

@@ -24,9 +24,9 @@
 
 #if HAS_PRUSA_MMU1
 
-#include "../MarlinCore.h"
-#include "../module/planner.h"
-#include "../module/stepper.h"
+#include "../../MarlinCore.h"
+#include "../../module/planner.h"
+#include "../../module/stepper.h"
 
 void mmu_init() {
   SET_OUTPUT(E_MUX0_PIN);