Add configurable beep for UltiPanel.

Marlin/ultralcd_implementation_hitachi_HD44780.h

 	#endif
 #elif defined(BEEPER) && BEEPER > -1
     SET_OUTPUT(BEEPER);
+	#if !defined(LCD_FEEDBACK_FREQUENCY_HZ) || !defined(LCD_FEEDBACK_FREQUENCY_DURATION_MS)
     for(int8_t i=0;i<10;i++)
     {
       WRITE(BEEPER,HIGH);
       delayMicroseconds(100);
       WRITE(BEEPER,LOW);
       delayMicroseconds(100);
-    }
+    }
+    #else
+    for(int8_t i=0;i<(LCD_FEEDBACK_FREQUENCY_DURATION_MS / (1000 / LCD_FEEDBACK_FREQUENCY_HZ));i++)
+    {
+      WRITE(BEEPER,HIGH);
+      delayMicroseconds(1000000 / LCD_FEEDBACK_FREQUENCY_HZ / 2);
+      WRITE(BEEPER,LOW);
+      delayMicroseconds(1000000 / LCD_FEEDBACK_FREQUENCY_HZ / 2);
+    }
+    #endif
 #endif
 }