ARM: dts: s5pv210: remove unused Atmel touchscreen properties in Goni

The Atmel bindings and driver do not use custom properties like
x/y-size, burst length, threshold and so on.  The driver gets necessary
data from the device directly.  Remove unused properties to fix
dtbs_check warning:

  arch/arm/boot/dts/s5pv210-goni.dt.yaml: touchscreen@4a:
    'atmel,burst-length', 'atmel,orientation', 'atmel,threshold', 'atmel,x-line', 'atmel,x-size',
    'atmel,y-line', 'atmel,y-size' do not match any of the regexes

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210506152044.37579-1-krzysztof.kozlowski@canonical.com