* [480x272] Fix compiler warnings with awkward extern define in layout.h.
* [firmware][misc] Fix build error with undefined SPLASH; Fix 128x64 syntax error in model_setup.cpp; Fix compiler warning on static init in diskio.cpp.
* [480x272] Revert "Fix compiler warnings with awkward extern define in layout.h." and modify lcd::drawSource() to use mixsrc_t for consistency.
This reverts commit d85d994c877a94c1933c6ece806565ca822d0f54.
* [firmware] Cleanup struct init in diskio modules.