arm64/dts: qcom: sdm845: Use RPMH_CE_CLK macro directly

In commit 3e482859 ("dts: qcom: sdm845: Add dt entries
to support crypto engine."), we decided to use the value indicated
by constant RPMH_CE_CLK rather than using it directly.

Now that the same RPMH clock value might be used for other
SoCs (in addition to sdm845), let's use the constant
RPMH_CE_CLK to make sure that this dtsi is compatible with the
other qcom ones.

Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Rob Herring <robh+dt@kernel.org>
Reviewed-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Bhupesh Sharma <bhupesh.sharma@linaro.org>