octeon: n821: sysupgrade for Cisco vEdge 1000

octeon: n821: sysupgrade for Cisco vEdge 1000

This commit adds the logic required to install OpenWrt on a
Cisco/Viptela vEdge 1000 while nicely integrating with the already
present bootloader and making it possible to roll back to stock OS.

The vEdge 1000 has a built-in SSD with a ext2 partition from which
the stock u-boot boots the Linux kernel from.

In order for Linux not to be confused about which partition the root
file system is on, there are some tricks needed to ensure the partition
is identifiable at boot time. For this we use blkid as part of the
scripts, and sfdisk as part of the manual installation process
documented on the wiki. Thus, those packages have been added as a
platform dependency. Finally, the u-boot environment is updated which
requires the use of uboot-envtools.

Tested on a Cisco vEdge 1000.

Signed-off-by: Christian Svensson <blue@cmd.nu>
Link: https://github.com/openwrt/openwrt/pull/16140
Signed-off-by: Robert Marko <robimarko@gmail.com>