LVGL: Multiple Displays

[towen]

Is your feature request related to a problem? Please describe.
It does not appear to be possible to use multiple displays with LVGL in Zephyr, even though LVGL itself supports multiple displays.
In modules/lvgl/lvgl.c zephyr is hardcoded to reference one display device:
#define DISPLAY_NODE DT_CHOSEN(zephyr_display)

Describe the solution you'd like
If not using CONFIG_LV_Z_AUTO_INIT, then LVGL could be initialised manually with two separate contexts, using different display devices.
Instead of simply calling lvgl_init(), we could call a new function lvgl_init_display(const struct device *display_dev)

Describe alternatives you've considered
lvgl.c uses unencapsulated variables (display and disp_data) and would need to be rewritten.. There are various KConfigs to define display settings (colour depth, etc) so supporting multiple different displays may be difficult, but multiple identical displays should be possible with less effort.