drm/stm: ltdc: update hardware error management

drm/stm: ltdc: update hardware error management

The latest hardware version (0x40100) supports a hardware threshold
register (aka FUTR) to trigger a fifo underrun interrupt.
A software threshold has been implemented for other hardware versions.
The threshold is set to 128 by default.

Signed-off-by: Yannick Fertre <yannick.fertre@foss.st.com>
Signed-off-by: Philippe Cornu <philippe.cornu@foss.st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220603134654.594373-1-yannick.fertre@foss.st.com