ramips: add broken-flash-reset for HLK-7621A EvB

This is needed because the HLK-7621 EvB has 32MB of flash,
so it will have to use 4B addressing and the
broken-flash-reset hack has to be used to be able to reboot.

Signed-off-by: Wout Bertrums <wout@wbnet.eu>
[copied github message into commit message]
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>

target/linux/ramips/dts/mt7621_hilink_hlk-7621a-evb.dts

@@ -27,6 +27,7 @@
 		compatible = "jedec,spi-nor";
 		reg = <0>;
 		spi-max-frequency = <44000000>;
+		broken-flash-reset;
 
 		partitions {
 			compatible = "fixed-partitions";