ipq40xx: increase SPI frequency for Zyxel NBG6617

The mx25l25635f supports clock speed up to 50Mhz.

Also remove obsolete "mx25l25635f" hack and rename
the matching device-tree flash node.

Signed-off-by: Dmitry Tunin <[email protected]>
[mention node rename as well. chip is very very likely
always the "f" revision for all NBG6617]
Signed-off-by: Christian Lamparter <[email protected]>

target/linux/ipq40xx/files/arch/arm/boot/dts/qcom-ipq4018-nbg6617.dts

@@ -210,10 +210,10 @@
 	status = "okay";
 	cs-gpios = <&tlmm 54 GPIO_ACTIVE_HIGH>;
 
-	mx25l25635f@0 {
-		compatible = "mx25l25635f", "jedec,spi-nor";
+	flash@0 {
+		compatible = "jedec,spi-nor";
 		reg = <0>;
-		spi-max-frequency = <24000000>;
+		spi-max-frequency = <50000000>;
 		status = "okay";
 		m25p,fast-read;