drm/exynos/hdmi: add 85.5MHz pixel clock for v14 HDMI PHY

Configuration details from Samsung. This enables 1366x768@60Hz,
which also needs the 256px timing hack to work around a mixer
limitation.

Signed-off-by: Daniel Drake <drake@endlessm.com>
Signed-off-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
[a.hajda@samsung.com: rebased onto proposed patchset]
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>