imx: kontron-sl-mx8mm: Migrate to use CONFIG_EXTRA_ENV_TEXT

Move the environment from the board header to a separate text file
and also drop those variables that are already set in env_default.h
from the Kconfig options.

Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: Fabio Estevam <festevam@denx.de>
diff --git a/board/kontron/sl-mx8mm/sl-mx8mm.env b/board/kontron/sl-mx8mm/sl-mx8mm.env
new file mode 100644
index 0000000..ef6fc1f
--- /dev/null
+++ b/board/kontron/sl-mx8mm/sl-mx8mm.env
@@ -0,0 +1,7 @@
+kernel_addr_r=0x42000000
+fdt_addr_r=0x48000000
+fdtoverlay_addr_r=0x49000000
+ramdisk_addr_r=0x48080000
+scriptaddr=0x40000000
+pxefile_addr_r=0x40100000
+dfu_alt_info=sf 0:0=flash-bin raw 0x400 0x1f0000
diff --git a/include/configs/kontron-sl-mx8mm.h b/include/configs/kontron-sl-mx8mm.h
index 622ab59..a2aedef 100644
--- a/include/configs/kontron-sl-mx8mm.h
+++ b/include/configs/kontron-sl-mx8mm.h
@@ -50,20 +50,6 @@
 #define CONFIG_MALLOC_F_ADDR		0x930000
 #endif
 
-#define ENV_MEM_LAYOUT_SETTINGS \
-	"loadaddr=" __stringify(CONFIG_SYS_LOAD_ADDR) "\0" \
-	"kernel_addr_r=0x42000000\0" \
-	"fdt_addr_r=0x48000000\0" \
-	"fdtoverlay_addr_r=0x49000000\0" \
-	"ramdisk_addr_r=0x48080000\0" \
-	"scriptaddr=0x40000000\0"\
-	"pxefile_addr_r=0x40100000\0"
-
-#define CONFIG_EXTRA_ENV_SETTINGS \
-	"dfu_alt_info=sf 0:0=flash-bin raw 0x400 0x1f0000\0" \
-	"bootdelay=3\0" \
-	"hostname=" CONFIG_HOSTNAME "\0" \
-	ENV_MEM_LAYOUT_SETTINGS \
-	BOOTENV
+#define CONFIG_EXTRA_ENV_SETTINGS BOOTENV
 
 #endif /* __KONTRON_MX8MM_CONFIG_H */