dt-bindings: display: sun4i-drm: Add LVDS properties

Some clocks and resets supposed to drive the LVDS logic in the display
engine have been overlooked when the driver was first introduced.

Add those additional resources to the binding, and we'll deal with the ABI
stability in the code.

Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Link: https://patchwork.freedesktop.org/patch/msgid/ddbde28fe2e4f21412974e4c69fbfe1c5ff9383f.1513854122.git-series.maxime.ripard@free-electrons.com