BTN_ENC_EN for many boards (#19890)

Enables CHECK_ENCODER_ACTIVE_SIGNAL for many more boards.

Co-authored-by: Scott Lahteine <thinkyhead@users.noreply.github.com>
Co-authored-by: Jason Smith <jason.inet@gmail.com>

Marlin/src/pins/samd/pins_RAMPS_144.h

@@ -594,6 +594,10 @@
     #endif
   #endif // IS_NEWPANEL
 
+  #if ENABLED(REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER)
+    #define BTN_ENC_EN               LCD_PINS_D7  // Detect the presence of the encoder
+  #endif
+
 #endif // HAS_WIRED_LCD
 
 //