dt-bindings: net: dsa: Fix JSON pointer references

A JSON pointer reference to the entire document must not have a trailing
"/" and should be just a "#". The existing jsonschema package allows
these, but changes in 4.18 make allowed "$ref" URIs stricter and throw
errors on these references.

Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230718203202.1761304-1-robh@kernel.org


Signed-off-by: Paolo Abeni <pabeni@redhat.com>