gui: kconfig: Fix broken refs to LVGL_OBJ_PRELOAD_DEF_ANIMATION_*

The CONFIG_ prefixes were missing.

Found with a work-in-progress scripts/kconfig/lint.py check.

These are defined in lib/gui/lvgl/Kconfig.objects.

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>