Replace legacy MMS114 touchscreen properties to fix dtschema warnings:

  arch/arm/boot/dts/exynos4412-n710x.dt.yaml: touchscreen@48:
    'x-size', 'y-size' do not match any of the regexes: 'pinctrl-[0-9]+'
  arch/arm/boot/dts/exynos4412-n710x.dt.yaml: touchscreen@48:
    'touchscreen-size-x' is a required property
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210505135941.59898-2-krzysztof.kozlowski@canonical.com