media: dt-bindings: media: venus: delete old binding document

After transitioning to YAML DT schema we don't need this old-style
document.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>