Integrate meta-guf-distro/cherry-pick-a9d370f1
fng-install:u-boot: Fix installation on devices without u-boot environment
The install script backups some variables from the existing u-boot environment before overwriting it. This failed for devices where no environment was available yet, which lead to stop the update with error. This case is now ignored and the installation continues without backup in this case.
(cherry picked from commit a9d370f1225eebe42f367b7f3ae454b52a8961cb)