dt-bindings: watchdog: qcom-wdt: require fallback for IPQ4019

The device specific compatibles ("qcom,kpss-wdt-ipq4019") should be
follwed by fallback "qcom,kpss-wdt", which is actually used by Linux
driver for binding.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20221212163532.142533-1-krzysztof.kozlowski@linaro.org


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>