ARM: dts: imx6q-bx50v3: fix at25 spi-clk frequency issue

Change the maxium spi clock frequency from 20MHz to 10MHz to meet the
operation voltage range requirement recommended in AT25 datasheet.
Signed-off-by: NKen Lin <yungching0725@gmail.com>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6q-bx50v3.dtsi

@@ -102,7 +102,7 @@
 
 	m25_eeprom: m25p80@0 {
 		compatible = "atmel,at25";
-		spi-max-frequency = <20000000>;
+		spi-max-frequency = <10000000>;
 		size = <0x8000>;
 		pagesize = <64>;
 		reg = <0>;