arm64: dts: imx8mm-kontron: Disable pullups for onboard UART signals on BL board

These signals are actively driven by the SoC or by the onboard
transceiver. There's no need to enable the internal pull resistors
and due to silicon errata ERR050080 let's disable the internal ones
to prevent any unwanted behavior in case they wear out.

Fixes: 8668d8b2 ("arm64: dts: Add the Kontron i.MX8M Mini SoMs and baseboards")
Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm-kontron-bl.dts

@@ -292,19 +292,19 @@ MX8MM_IOMUXC_SPDIF_RX_PWM2_OUT			0x19
 
 	pinctrl_uart1: uart1grp {
 		fsl,pins = <
-			MX8MM_IOMUXC_SAI2_RXC_UART1_DCE_RX		0x140
-			MX8MM_IOMUXC_SAI2_RXFS_UART1_DCE_TX		0x140
-			MX8MM_IOMUXC_SAI2_RXD0_UART1_DCE_RTS_B		0x140
-			MX8MM_IOMUXC_SAI2_TXFS_UART1_DCE_CTS_B		0x140
+			MX8MM_IOMUXC_SAI2_RXC_UART1_DCE_RX		0x0
+			MX8MM_IOMUXC_SAI2_RXFS_UART1_DCE_TX		0x0
+			MX8MM_IOMUXC_SAI2_RXD0_UART1_DCE_RTS_B		0x0
+			MX8MM_IOMUXC_SAI2_TXFS_UART1_DCE_CTS_B		0x0
 		>;
 	};
 
 	pinctrl_uart2: uart2grp {
 		fsl,pins = <
-			MX8MM_IOMUXC_SAI3_TXFS_UART2_DCE_RX		0x140
-			MX8MM_IOMUXC_SAI3_TXC_UART2_DCE_TX		0x140
-			MX8MM_IOMUXC_SAI3_RXD_UART2_DCE_RTS_B		0x140
-			MX8MM_IOMUXC_SAI3_RXC_UART2_DCE_CTS_B		0x140
+			MX8MM_IOMUXC_SAI3_TXFS_UART2_DCE_RX		0x0
+			MX8MM_IOMUXC_SAI3_TXC_UART2_DCE_TX		0x0
+			MX8MM_IOMUXC_SAI3_RXD_UART2_DCE_RTS_B		0x0
+			MX8MM_IOMUXC_SAI3_RXC_UART2_DCE_CTS_B		0x0
 		>;
 	};