arm64: dts: imx8mq-librem5: Limit the max sdio frequency

This is needed for the 1LV Cyress WiFi module to probe correctly.
It also helps improve GNSS sensitivity.
Signed-off-by: NAngus Ainslie <angus@akkea.ca>
Signed-off-by: NMartin Kepplinger <martin.kepplinger@puri.sm>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi

@@ -1237,6 +1237,7 @@
 	mmc-pwrseq = <&usdhc2_pwrseq>;
 	post-power-on-delay-ms = <1000>;
 	cd-gpios = <&gpio2 12 GPIO_ACTIVE_LOW>;
+	max-frequency = <50000000>;
 	disable-wp;
 	cap-sdio-irq;
 	keep-power-in-suspend;