dt-bindings: arm: cpus: Document qcom,msm8916-smp enable-method

Since MSM8916 is an ARM v8 64-bit SoC the CPU cores are normally booted
using "psci" or "spin-table". Unfortunately, some devices come with signed
32-bit-only firmware without ARM64 and PSCI support. This setup is easy to
support since it's very similar to older 32-bit only Qualcomm SoCs
(e.g. MSM8226) and only requires adding a few new definitions to already
existing drivers.

Document the qcom,msm8916-smp enable-method. It is actually just an alias
of qcom,msm8226-smp since it should be implemented identically.
The enable-method is only valid on ARM32 and must not be used on ARM64.
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211004204955.21077-8-stephan@gerhold.net

Documentation/devicetree/bindings/arm/cpus.yaml

@@ -210,6 +210,8 @@ properties:
           - qcom,kpss-acc-v1
           - qcom,kpss-acc-v2
           - qcom,msm8226-smp
+          # Only valid on ARM 32-bit, see above for ARM v8 64-bit
+          - qcom,msm8916-smp
           - renesas,apmu
           - renesas,r9a06g032-smp
           - rockchip,rk3036-smp
@@ -294,7 +296,8 @@ properties:
       Specifies the ACC* node associated with this CPU.
 
       Required for systems that have an "enable-method" property
-      value of "qcom,kpss-acc-v1", "qcom,kpss-acc-v2" or "qcom,msm8226-smp"
+      value of "qcom,kpss-acc-v1", "qcom,kpss-acc-v2", "qcom,msm8226-smp" or
+      "qcom,msm8916-smp".
 
       * arm/msm/qcom,kpss-acc.txt