dt-bindings: panel: ili9341: correct indentation

Correct indentation warning:
  ilitek,ili9341.yaml:25:9: [warning] wrong indentation: expected 10 but found 8 (indentation)
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210819101020.26368-1-krzysztof.kozlowski@canonical.com