ramips: mt7621-dts: enable flow control on port@6

Flow control needs to be enabled on both sides to work.
It is already enabled on gmac0, enable it on port@6 too.

Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Tested-by: Sungbo Eo <mans0n@gorani.run>

target/linux/ramips/dts/mt7621.dtsi

@@ -532,6 +532,7 @@
 						fixed-link {
 							speed = <1000>;
 							full-duplex;
+							pause;
 						};
 					};
 				};