dt-bindings: net: dsa: convert ocelot.txt to dt-schema

dt-bindings: net: dsa: convert ocelot.txt to dt-schema

Replace the free-form description of device tree bindings for VSC9959
and VSC9953 with a YAML formatted dt-schema description. This contains
more or less the same information, but reworded to be a bit more
succint.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Maxim Kochetkov <fido_max@inbox.ru>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220913125806.524314-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>