arm64: dts: qcom: sm6375-pdx225: add fixed touchscreen AVDD regulator

arm64: dts: qcom: sm6375-pdx225: add fixed touchscreen AVDD regulator

The Samsung S6SY761 touchscreen bindings expect AVDD regulator which is
missing in the Sony Xperia PDX225 DTS.  There is however pinctrl setting
for in the touchscreen device node with similar name: "avdd", so assume
author wanted to control a fixed regulator with a GPIO.

This fixes dtbs_check warning:

  sm6375-sony-xperia-murray-pdx225.dtb: touchscreen@48: 'avdd-supply' is a required property

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20231111164229.63803-6-krzysztof.kozlowski@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>