arm64: dts: qcom: msm8996: Correct apr-domain property

The domain specifier was changed from using "reg" to "qcom,apr-domain",
update the dts accordingly.

Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>