arm: dts: qcom: Add aliases for PMICs

Add an alias for the PMICs found on qcom 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>