dt-bindings: firmware: scm: Add sc7280 support

Add compatible for sc7280 SoC
Signed-off-by: NRajendra Nayak <rnayak@codeaurora.org>
Reviewed-by: NStephen Boyd <swboyd@chromium.org>
Acked-by: NRob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1615461961-17716-3-git-send-email-rnayak@codeaurora.orgSigned-off-by: NBjorn Andersson <bjorn.andersson@linaro.org>

Documentation/devicetree/bindings/firmware/qcom,scm.txt

@@ -20,6 +20,7 @@ Required properties:
  * "qcom,scm-msm8996"
  * "qcom,scm-msm8998"
  * "qcom,scm-sc7180"
+ * "qcom,scm-sc7280"
  * "qcom,scm-sdm845"
  * "qcom,scm-sm8150"
  * "qcom,scm-sm8250"