ARM: dts: qcom: msm8226: add power domains

Add a node for the power domain controller found in MSM8226.

At the same time remove any existing usages of pm8226_s1 as this
regulator is now handled by power domains.

Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220220223004.507739-3-luca@z3ntu.xyz