common: edid: Search for valid timing in extension block

One of my monitors have only 4k@60 timing in base EDID block which is
out of range for devices with HDMI 1.4. It turns out that it has
additional detailed timings in CTA-861 Extension Block and two of them
are appropriate for HDMI 1.4.

Add additional search for valid detailed timing in extension block.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Acked-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>