Make encoderLine signed for proper compares

Marlin/ultralcd.cpp

     ENCODER_DIRECTION_MENUS(); \
     encoderRateMultiplierEnabled = false; \
     if (encoderPosition > 0x8000) encoderPosition = 0; \
-    uint8_t encoderLine = encoderPosition / ENCODER_STEPS_PER_MENU_ITEM; \
+    int8_t encoderLine = encoderPosition / ENCODER_STEPS_PER_MENU_ITEM; \
     NOMORE(encoderTopLine, encoderLine); \
     uint8_t _lineNr = encoderTopLine, _menuItemNr; \
     CODE; \