README.hardware: update Edgerouter section

Updated image creation instructions. Used wic images instead
of manually putting rootfs and kernel to SD card.

[YOCTO #8719]

(From meta-yocto rev: 2b030a6061a33334bec63fce23447cbbe1846c86)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

README.hardware

@@ -301,75 +301,25 @@ Load the kernel, and boot the system as follows:
  => tftp tftp $loadaddr vmlinux
  => bootoctlinux $loadaddr coremask=0x3 root=/dev/nfs rw nfsroot=<nfsroot ip>:<rootfs path> ip=<board ip>:<server ip>:<gateway ip>:<netmask>:edgerouter:eth0:off mtdparts=phys_mapped_flash:512k(boot0),512k(boot1),64k@3072k(eeprom)
 
---- Booting from USB root ---
+--- Booting from USB disk ---
 
 To boot from the USB disk, you either need to remove it from the edgerouter
 box and populate it from another computer, or use a previously booted NFS
 image and populate from the edgerouter itself.
 
-Type 1: Mounted USB disk
-------------------------
-
-To boot from the USB disk there are two available partitions on the factory
-USB storage. The rest of this guide assumes that these partitions are left
-intact. If you change the partition scheme, you must update your boot method
-appropriately.
-
-The standard partitions are:
-
-  - 1: vfat partition containing factory kernels
-  - 2: ext3 partition for the root filesystem.
-
-You can place the kernel on either partition 1, or partition 2, but the roofs
-must go on partition 2 (due to its size).
-
-Note: If you place the kernel on the ext3 partition, you must re-create the
-      ext3 filesystem, since the factory u-boot can only handle 128 byte inodes and
-      cannot read the partition otherwise.
+Type 1: Use partitioned image
+-----------------------------
 
 Steps:
 
  1. Remove the USB disk from the edgerouter and insert it into a computer
     that has access to your build artifacts.
 
- 2. Copy the kernel image to the USB storage (assuming discovered as 'sdb' on
-    the development machine):
+ 2. Flash the image.
 
-    2a) if booting from vfat
- 
-        # mount /dev/sdb1 /mnt
-        # cp tmp/deploy/images/edgerouter/vmlinux /mnt
-        # umount /mnt
+    # dd core-image-minimal-edgerouter.wic of=/dev/sdb
 
-    2b) if booting from ext3
-
-        # mkfs.ext3 -I 128 /dev/sdb2
-        # mount /dev/sdb2 /mnt
-        # mkdir /mnt/boot
-        # cp tmp/deploy/images/edgerouter/vmlinux /mnt/boot
-        # umount /mnt
-
- 3. Extract the rootfs to the USB storage ext3 partition
-
-        # mount /dev/sdb2 /mnt
-        # tar -xvjpf core-image-minimal-XXX.tar.bz2 -C /mnt
-        # umount /mnt
-
- 4. Reboot the board and press a key on the terminal when prompted to get to the U-Boot
-    command line:
-
- 5. Load the kernel and boot:
-
-    5a) vfat boot
-
-         => fatload usb 0:1 $loadaddr vmlinux
-
-    5b) ext3 boot
-
-         => ext2load usb 0:2 $loadaddr boot/vmlinux
- 
-    => bootoctlinux $loadaddr coremask=0x3 root=/dev/sda2 rw rootwait mtdparts=phys_mapped_flash:512k(boot0),512k(boot1),64k@3072k(eeprom)
- 
+ 3. Insert USB disk into the edgerouter and boot it.
 
 Type 2: NFS
 -----------