dt-bindings: display: bridge: tc358867: Add interrupt property

This bridge has an interrupt line for event signaling. Add the
corresponding property.

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230718084411.1189831-1-alexander.stein@ew.tq-group.com