imx: add i.MX8MN DDR4 board support

Support pinctrl/clk/sdhc, include ddr4 timing data.

Log:
U-Boot SPL 2019.10-rc3-00356-g497c500423-dirty (Sep 16 2019 - 10:54:58 +0800)
Normal Boot
Trying to boot from BOOTROM
image offset 0x8000, pagesize 0x200, ivt offset 0x0

U-Boot 2019.10-rc3-00356-g497c500423-dirty (Sep 16 2019 - 10:54:58 +0800)

CPU:   Freescale i.MX8MNano rev1.0 at 24 MHz
Reset cause: POR
Model: NXP i.MX8MNano DDR4 EVK board
DRAM:  2 GiB
MMC:   FSL_SDHC: 1, FSL_SDHC: 2
Loading Environment from MMC... *** Warning - bad CRC, using default environment

In:    serial
Out:   serial
Err:   serial
Net:   No ethernet found.
Hit any key to stop autoboot:  0

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/dts/imx8mm-evk.dts b/arch/arm/dts/imx8mm-evk.dts
index faefb71..ef249ff 100644
--- a/arch/arm/dts/imx8mm-evk.dts
+++ b/arch/arm/dts/imx8mm-evk.dts
@@ -464,7 +464,7 @@
 			MX8MM_IOMUXC_NAND_CE2_B_USDHC3_DATA5		0x1d0
 			MX8MM_IOMUXC_NAND_CE3_B_USDHC3_DATA6		0x1d0
 			MX8MM_IOMUXC_NAND_CLE_USDHC3_DATA7		0x1d0
-			MX8MM_IOMUXC_NAND_CE1_B_USDHC3_STROBE 		0x190
+			MX8MM_IOMUXC_NAND_CE1_B_USDHC3_STROBE		0x190
 		>;
 	};
 
@@ -480,7 +480,7 @@
 			MX8MM_IOMUXC_NAND_CE2_B_USDHC3_DATA5		0x1d4
 			MX8MM_IOMUXC_NAND_CE3_B_USDHC3_DATA6		0x1d4
 			MX8MM_IOMUXC_NAND_CLE_USDHC3_DATA7		0x1d4
-			MX8MM_IOMUXC_NAND_CE1_B_USDHC3_STROBE 		0x194
+			MX8MM_IOMUXC_NAND_CE1_B_USDHC3_STROBE		0x194
 		>;
 	};
 
@@ -496,7 +496,7 @@
 			MX8MM_IOMUXC_NAND_CE2_B_USDHC3_DATA5		0x1d6
 			MX8MM_IOMUXC_NAND_CE3_B_USDHC3_DATA6		0x1d6
 			MX8MM_IOMUXC_NAND_CLE_USDHC3_DATA7		0x1d6
-			MX8MM_IOMUXC_NAND_CE1_B_USDHC3_STROBE 		0x196
+			MX8MM_IOMUXC_NAND_CE1_B_USDHC3_STROBE		0x196
 		>;
 	};