samples: drivers: video: capture_to_lvgl: Migrate to LVGL v9.2

Adjust the Kconfig symbols of the capture to lvgl sample. LV_MEM_CUSTOM has
been removed in v9.0 and LV_USE_IMG has been changed to LV_USE_IMAGE.
Fix the changed fields for the image descriptor struct.

Signed-off-by: Fabian Blatz <fabianblatz@gmail.com>