video: meson: dw-hdmi: add EDID mode filtering to only select supported modes

Add support for the new mode_valid() display op to filter out unsupported
display DMT timings.

This is useful when connected to 4k displays, since we only support DMT
monitors up to 1920x1080, the 4k native timings are discarded to select
supported timings.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>