Define Z_MIN_PROBE_PIN for Cohesion 3D Remix

Marlin/src/pins/lpc1769/pins_COHESION3D_REMIX.h

 #define Z_MAX_PIN          P1_29   // 10k pullup to 3.3V
 
 //
+// Z Probe (when not Z_MIN_PIN)
+//
+#ifndef Z_MIN_PROBE_PIN
+  #define Z_MIN_PROBE_PIN  P1_29
+#endif
+
+//
 // Steppers
 //
 #define X_STEP_PIN         P2_00