modules: lvgl: add multi-display support in Zephyr

Add multi-display support in Zephyr ontop of LVGL which already supports
it.

This change allows for creating buffers and structures for each display
statically and automatically from deviceTree info, and call LV init
routines for each display

Signed-off-by: Abderrahmane JARMOUNI <git@jarmouni.me>