modules: lvgl: Add support for frame rounder callback

Add support for LVGL rounder callback function. Sometimes,
either the underlying display controller and/or the LCD host
controller might impose restrictions on frame resolution.
For instance, the E1394AA65A display model should impose that
either axis of a frame be multiple of 2 pixels or the Renesas
LCD controller of the DA1469x SoC, should impose that the
stride value, number of bytes between consecutive frame lines,
be multiple of 4 bytes.

Signed-off-by: Ioannis Karachalios <ioannis.karachalios.px@renesas.com>