arm64: dts: qcom: msm8916-samsung-a2015: Add touchscreen regulator

A3U and A5U both use an extra touchscreen LDO regulator
that provides 3.3V for the touch screen controller.

Add it as fixed regulator to the common include.

Cc: Michael Srba <Michael.Srba@seznam.cz>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20200426140642.204395-4-stephan@gerhold.net


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