dt-bindings: clock: Cleanup qcom,videocc bindings for sdm845/sc7180

This makes the qcom,videocc bindings match the recent changes to the
dispcc and gpucc.

1. Switched to using "bi_tcxo" instead of "xo".

2. Adds a description for the XO clock.  Not terribly important but
   nice if it cleanly matches its cousins.

3. Updates the example to use the symbolic name for the RPMH clock and
   also show that the real devices are currently using 2 address cells
   / size cells and fixes the spacing on the closing brace.

4. Split into 2 files.  In this case they could probably share one
   file, but let's be consistent.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lkml.kernel.org/r/20200203103049.v4.11.I27bbd90045f38cd3218c259526409d52a48efb35@changeid


Signed-off-by: Stephen Boyd <sboyd@kernel.org>