I take the liberty of a small contradiction 
LVGL doesn’t know anything about the connected display hardware.
LVGL just needs to know about the width and height and color depth for rendering into a buffer.
How the buffer content is transferred into a real display is not of interest for lvgl.
Transferring the data to the real display hardware is done in the flush callback function.
As I understand, Zheckiss question would be more relevant to be asked in an ESP32 forum.
As how to configure ESP32 to use one 8080 interface for two displays separated by two different CS (chip select) pins.
The flush function then has just to decide which of the area pixel has to be send to which display. And that seems to be more or less easy.