This way MTD "bootfs" partition will be always 8+ MiB. This should be
enough for any custom / future firmware to fit its bootfs (e.g. big
kernel) without having to repertition whole flash. That way we can
preserve UBI and its erase counters during sysupgrade.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
(cherry picked from commit ca9b1f15c4)