SMD edge contains subnodes representing devices related to the remote
processor.  With limietd number of remote processors, there is a limited
set of such devices.

List all of them in smd-edge bindings so schema can strictly check for
subnodes.

Additional benefit is requirement of "qcom,smd-channels" for such
subnodes, because their schema cannot enforce it (few devices like APR
or FastRPC can be part of either SMD or GLINK edge).
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220909125403.803158-8-krzysztof.kozlowski@linaro.orgSigned-off-by: Rob Herring <robh@kernel.org>