arm64: dts: qcom: msm8916-huawei-g7: Add touchscreen

The Huawei Ascend G7 has a Synaptics "C199HW-006" touchscreen,
supplied by pm8916_l17 and pm8916_l16. Add it to the device tree
and reduce the maximum allowed voltage for pm8916_l16 to 1.8V since
we really should not use more for an I/O supply.

Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20210514104328.18756-2-stephan@gerhold.net


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