ramips: increase SPI frequency for ELECOM WRC-GST devices

Increase the SPI frequency for ELECOM WRC-1900GST and WRC-2533GST
to 40 MHz by updating the common DTSI file.

Signed-off-by: INAGAKI Hiroshi <musashino.open@gmail.com>
[WRC-1900GST]
Acked-by: NOGUCHI Hiroshi <drvlabo@gmail.com>
[split patch, adjust commit title/message]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/ramips/dts/mt7621_elecom_wrc-gst.dtsi

@@ -127,7 +127,7 @@
 	flash@0 {
 		compatible = "jedec,spi-nor";
 		reg = <0>;
-		spi-max-frequency = <10000000>;
+		spi-max-frequency = <40000000>;
 
 		partitions {
 			compatible = "fixed-partitions";