neutrino: explicitly include vfd/lcd header

Instead of including it everywhere through global.h, just include
the lcd/vfd header where needed. Add a tiny helper header "display.h"
to divert between vfd.h (coolstream) and lcdd.h (everything else).

src/driver/volume.cpp

@@ -38,6 +38,7 @@
 #include <system/helpers.h>
 #include <daemonc/remotecontrol.h>
 #include <driver/volume.h>
+#include <driver/display.h>
 #include <gui/audiomute.h>
 #include <zapit/zapit.h>