ramips: lower re305-v3 spi-max-frequency

Fix flash I/O instability observed in newer devices with cFeon
QH64A-104HIP (detected as en25qh64).

Ref: https://forum.openwrt.org/t/support-for-tp-link-re305-v3/75893/91

Reported-by: Dimitri Souza <[email protected]>
Tested-by: Dimitri Souza <[email protected]>
Signed-off-by: Joe Mullally <[email protected]>
[alter commit-message - target master]
Signed-off-by: David Bauer <[email protected]>

target/linux/ramips/dts/mt7628an_tplink_re305-v3.dts

@@ -13,7 +13,7 @@
 	flash@0 {
 		compatible = "jedec,spi-nor";
 		reg = <0>;
-		spi-max-frequency = <50000000>;
+		spi-max-frequency = <10000000>;
 
 		partitions {
 			compatible = "fixed-partitions";