media: dt-bindings: qcom-sc7180-venus: move video-firmware here

media: dt-bindings: qcom-sc7180-venus: move video-firmware here

As SC7180 is the only remaining user of the non-TZ / non-PAS setup which
uses the video-firmware subnode, move its definition from the common
schema to the SC7180-specific one.

These properties do not accurately describe the hardware.  Future
platforms that are going to support non-TZ setup will use different
semantics and different DT ABI (using the iommu-map property).

Reviewed-by: Vikash Garodia <vikash.garodia@oss.qualcomm.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Bryan O'Donoghue <bod@kernel.org>