Make lcd function static

Firmware/ultralcd.cpp

@@ -471,7 +471,7 @@ void lcdui_print_extruder(void)
 }
 
 // Print farm number (5 chars total)
-void lcdui_print_farm(void)
+static void lcdui_print_farm(void)
 {
 	lcd_printf_P(_N(" FRM "));
 }