arm64: dts: qcom: Alias pm8916 on msm8916 devices

Add an alias for pm8916 on msm8916 based SoCs so that the newly
updated dtbTool can find the pmic compatible string and add the
pmic-id element to the QCDT header.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Andy Gross <agross@codeaurora.org>