Followup to BLTouch (#13422)

Marlin/src/feature/bedlevel/mbl/mesh_bed_leveling.h

@@ -34,6 +34,9 @@ enum MeshLevelingState : char {
 
 #define MESH_X_DIST ((MESH_MAX_X - (MESH_MIN_X)) / (GRID_MAX_POINTS_X - 1))
 #define MESH_Y_DIST ((MESH_MAX_Y - (MESH_MIN_Y)) / (GRID_MAX_POINTS_Y - 1))
+#define _GET_MESH_X(I) mbl.index_to_xpos[I]
+#define _GET_MESH_Y(J) mbl.index_to_ypos[J]
+#define Z_VALUES_ARR mbl.z_values
 
 class mesh_bed_leveling {
 public:
@@ -118,5 +121,3 @@ public:
 };
 
 extern mesh_bed_leveling mbl;
-
-#define Z_VALUES(X,Y) mbl.z_values[X][Y]