Minor pins cleanup

Marlin/src/pins/lpc1768/pins_BTT_SKR_V1_1.h

     #if AXIS_DRIVER_TYPE_X(TMC2130)
       #define X_CS_PIN                     P4_28
       #undef X_ENABLE_PIN
-      #define X_ENABLE_PIN                 -1
     #endif
 
     #if AXIS_DRIVER_TYPE_Y(TMC2130)
       #define Y_CS_PIN                     P2_00
       #undef Y_ENABLE_PIN
-      #define Y_ENABLE_PIN                 -1
     #endif
 
     #if AXIS_DRIVER_TYPE_Z(TMC2130)
       #define Z_CS_PIN                     P0_19
       #undef Z_ENABLE_PIN
-      #define Z_ENABLE_PIN                 -1
     #endif
 
     #if AXIS_DRIVER_TYPE_E0(TMC2130)
       #define E0_CS_PIN                    P2_12
       #undef E0_ENABLE_PIN
-      #define E0_ENABLE_PIN                -1
     #endif
 
     #if AXIS_DRIVER_TYPE_E1(TMC2130)
       #define E1_CS_PIN                    P0_10
       #undef E1_ENABLE_PIN
-      #define E1_ENABLE_PIN                -1
     #endif
 
   #else                                           // !SOFTWARE_DRIVER_ENABLE

Marlin/src/pins/ramps/pins_RIGIDBOARD.h

 // Misc. Functions
 //
 #undef PS_ON_PIN
-#define PS_ON_PIN                             -1
 
 //
 // LCD / Controller
 
   // Disable encoder
   #undef BTN_EN1
-  #define BTN_EN1                             -1
   #undef BTN_EN2
-  #define BTN_EN2                             -1
 
   #undef SD_DETECT_PIN
   #define SD_DETECT_PIN                       22