dt-bindings: firmware: qcom: scm: add SSC_Q6 and ADSP_Q6 VMIDs

SSC_Q6 and ADSP_Q6 are used in the FastRPC driver for accessing
the secure world.

Signed-off-by: Dylan Van Assche <me@dylanvanassche.be>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230406173148.28309-3-me@dylanvanassche.be