video: stm32: stm32_ltdc: support several hardware versions

Register mapping & pixel formats depend on version of ltdc
display controller.

Signed-off-by: Yannick Fertre <yannick.fertre@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>