MLK-21173 ARM64: dts: fix imx8qxp-pinctrl iomuxc error

Because we add the partition reboot function, and assign all flexcan
pins to M4, A core cannot access flexcan pins for now.

LPUART3 uses flexcan pins before, so disable it to avoid this error:
imx8qxp-pinctrl iomuxc: pin_config_set op failed for pin 110

Signed-off-by: Clark Wang <xiaoning.wang@nxp.com>
(cherry picked from commit be821a84c44f6d8cf6e9a2573d214de91739dfdf)

arch/arm64/boot/dts/freescale/fsl-imx8qxp-mek-rpmsg.dtsi

@@ -206,3 +206,7 @@
 &flexspi0 {
 	status = "disabled";
 };
+
+&lpuart3 {
+	status = "disabled";
+};