dt-binding: gce: remove atomic_exec in mboxes property

There is not any client driver using this feature now,
so remove it from binding.
Signed-off-by: Bibby Hsieh <bibby.hsieh@mediatek.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

Documentation/devicetree/bindings/mailbox/mtk-gce.txt

@@ -14,13 +14,11 @@ Required properties:
 - interrupts: The interrupt signal from the GCE block
 - clock: Clocks according to the common clock binding
 - clock-names: Must be "gce" to stand for GCE clock
-- #mbox-cells: Should be 3.
-	<&phandle channel priority atomic_exec>
+- #mbox-cells: Should be 2.
+	<&phandle channel priority>
 	phandle: Label name of a gce node.
 	channel: Channel of mailbox. Be equal to the thread id of GCE.
 	priority: Priority of GCE thread.
-	atomic_exec: GCE processing continuous packets of commands in atomic
-		way.
 
 Required properties for a client device:
 - mboxes: Client use mailbox to communicate with GCE, it should have this
@@ -54,8 +52,8 @@ Example for a client device:
 
 	mmsys: clock-controller@14000000 {
 		compatible = "mediatek,mt8173-mmsys";
-		mboxes = <&gce 0 CMDQ_THR_PRIO_LOWEST 1>,
-			 <&gce 1 CMDQ_THR_PRIO_LOWEST 1>;
+		mboxes = <&gce 0 CMDQ_THR_PRIO_LOWEST>,
+			 <&gce 1 CMDQ_THR_PRIO_LOWEST>;
 		mutex-event-eof = <CMDQ_EVENT_MUTEX0_STREAM_EOF
 				CMDQ_EVENT_MUTEX1_STREAM_EOF>;
 		mediatek,gce-client-reg = <&gce SUBSYS_1400XXXX 0x3000 0x1000>,