arm64: dts: qcom: msm8916-pm8916: Stop using s1/l3 as regulators

s1 (VDDCX) and l3 (VDDMX) are now managed by rpmpd as power domains.
This allows us to vote for voltage corners instead of voting for raw
voltages. But we cannot manage these as regulator and power domain at
the same time: The votes by rpmpd would conflict with the ones from
the regulator driver.

All users of these regulators have been converted to power domains.
Make sure that no new users are added by removing s1 and l3 from
the regulator definitions.

This also allows us to remove the arbitrary voltage constraints
we have been using for these regulators. Not all of the voltages
listed there would actually have been safe for the boards.

Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20200916104135.25085-11-stephan@gerhold.net
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>