dt-bindings: mailbox: qcom,apcs-kpss-global: drop duplicated qcom,ipq8074-apcs-apps-global

qcom,ipq8074-apcs-apps-global compatible is listed in two places: with
and without fallback.  Drop the second case to match DTS.

Fixes: 34d8775a ("dt-bindings: mailbox: qcom,apcs-kpss-global: use fallbacks for few variants")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>