phycore_imx8mm: Switch to using env text files

Move the environment into the board directory and convert header to a
txt file. In addition, this patch also applies following changes:

- Change default nfsroot path to /srv/nfs due to compliance with Linux
FHS 3.0.

- Rename specific variables as stated in the bootstd documentation.
Renamed variables:
	fdt_addr => fdt_addr_r
	fdt_file => fdtfile

Signed-off-by: Yunus Bas <y.bas@phytec.de>

board/phytec/phycore_imx8mm/phycore_imx8mm.env

@@ -0,0 +1,51 @@
+console=ttymxc2,115200
+emmc_dev=2
+fdt_addr_r=0x48000000
+fdtfile=CONFIG_DEFAULT_FDT_FILE
+image=Image
+ip_dyn=yes
+loadimage=fatload mmc ${mmcdev}:${mmcpart} ${loadaddr} ${image}
+loadfdt=fatload mmc ${mmcdev}:${mmcpart} ${fdt_addr_r} ${fdtfile}
+mmcargs=
+	setenv bootargs console=${console}
+	root=/dev/mmcblk${mmcdev}p${mmcroot} rootwait rw
+mmcautodetect=yes
+mmcboot=
+	echo Booting from mmc ...;
+	run mmcargs;
+	if run loadfdt; then
+		if test ${dofitboot} = 1; then
+			booti ${loadaddr} - ${fdt_addr_r}
+		else
+			echo WARN: Cannot load the DT;
+		fi;
+	fi;
+mmcdev=CONFIG_SYS_MMC_ENV_DEV
+mmcpart=1
+mmcroot=2
+netargs=
+	setenv bootargs console=${console} root=/dev/nfs ip=dhcp
+	nfsroot=${serverip}:${nfsroot},v3,tcp
+netboot=
+	echo Booting from net ...;
+	if test ${ip_dyn} = yes; then
+		setenv get_cmd dhcp;
+	else
+		setenv get_cmd tftp;
+	fi;
+	${get_cmd} ${loadaddr} ${image};
+	run netargs;
+	if ${get_cmd} ${fdt_addr_r} ${fdtfile}; then
+		booti ${loadaddr} - ${fdt_addr_r};
+	else
+		echo WARN: Cannot load the DT;
+	fi;
+nfsroot=/srv/nfs
+update_bootimg=
+	mmc dev ${mmcdev};
+	if dhcp ${loadaddr} ${update_filepath}/${update_filename}; then
+		setexpr fw_sz ${filesize} / 0x200;
+		mmc write ${loadaddr} ${update_offset} ${fw_sz};
+	fi;
+update_filename=flash.bin
+update_offset=0x42