apm821xx: MX60(W): enable u-boot environment

This patch adds u-boot environment access to the MX60(W) target.
"The environment size is one NAND block (128KiB on Buckminster).
We allocate four NAND blocks to deal with bad blocks which may
exist in the saved  environment"

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>

package/boot/uboot-envtools/files/apm821xx

@@ -14,6 +14,9 @@ meraki,mr24)
 	ubootenv_add_uci_config "/dev/mtd1" "0x0" "0x4000" "0x4000" "4"
 	ubootenv_add_uci_config "/dev/mtd2" "0x0" "0x4000" "0x4000" "4"
 	;;
+meraki,mx60)
+	ubootenv_add_uci_config "/dev/mtd1" "0x0" "0x20000" "0x20000" "4"
+	;;
 esac
 
 config_load ubootenv