tridentfb: Add DDC support

Add DDC support for Trident cards.

Tested on TGUI9440, TGUI9680, 3DImage 9750, Blade3D 9880 and Blade XP.

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>