arm64: dts: fsl: add fsl,extts-fifo property for fman ptp

The 1588 timer supports external trigger timestamp FIFO on
FMan on QorIQ ARM platforms.
Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/qoriq-fman3-0.dtsi

@@ -81,4 +81,5 @@ ptp_timer0: ptp-timer@1afe000 {
 	reg = <0x0 0x1afe000 0x0 0x1000>;
 	interrupts = <GIC_SPI 44 IRQ_TYPE_LEVEL_HIGH>;
 	clocks = <&clockgen 3 0>;
+	fsl,extts-fifo;
 };