dt-bindings: soc: qcom: apr: document generic qcom,apr compatible

Document the qcom,apr compatible, used by Qualcomm Asynchronous Packet
Router driver.  There are no upstream DTSes using this compatible -
instead we have ones with APRv2 (qcom,apr-v2).  The driver does not make
distinction between both compatibles, which raises the question whether
the compatible is really needed.  Document it (as compatible with v2)
for completeness.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221201133637.46146-1-krzysztof.kozlowski@linaro.org