arm64: dts: qcom: msm8916-samsung-a3u: Add touch key regulators

The touch key MCU and LED is supplied by two separate fixed regulators
that can be enabled through GPIO 86 and 60. Add them to the device tree.

Signed-off-by: Michael Srba <Michael.Srba@seznam.cz>
[stephan: extend commit message]
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20210604172742.10593-2-stephan@gerhold.net


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>