mvebu: fixup Turris Omnia U-Boot environment

mvebu: fixup Turris Omnia U-Boot environment

Fixup dfa357a3de "mvebu: base-files: Update Turris Omnia U-Boot
environment" which should have included this file as well.

By rebasing the initial patch this file somehow disappeared.

Signed-off-by: Klaus Kudielka <klaus.kudielka@gmail.com>
Reviewed-by: Tomasz Maciej Nowak <tomek_n@o2.pl>
Tested-by: W. Michael Petullo <mike@flyn.org> (Turris Omnia "2020")
Tested-by: Klaus Kudielka <klaus.kudielka@gmail.com> (Turris Omnia)
[explain fixup in commit message]
Signed-off-by: Paul Spooren <mail@aparcar.org>
(backported from commit 485ce5bbe5cc33526e56817694a79a7d94160e01)
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>