ARM: dts: ls1021a: add 1588 external trigger stamp fifo support

This patch is to add external trigger stamp fifo support
for 1588 timer.
Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/arm/boot/dts/ls1021a.dtsi

@@ -706,6 +706,7 @@ ptp_clock@2d10e00 {
 			fsl,tmr-fiper1  = <999999995>;
 			fsl,tmr-fiper2  = <99990>;
 			fsl,max-adj     = <499999999>;
+			fsl,extts-fifo;
 		};
 
 		enet0: ethernet@2d10000 {