dt-bindings: clk: versaclock5: convert to yaml

Convert to yaml the VersaClock bindings document. The mapping between
clock specifier and physical pins cannot be described formally in yaml
schema, then keep it verbatim in the description field.

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Link: https://lore.kernel.org/r/20200723074112.3159-4-luca@lucaceresoli.net


Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>