Add support for TMDS Clock > 3.4GHz for HDMI2.0 display modes.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1549022873-40549-3-git-send-email-narmstrong@baylibre.com