The previous commit broke opkg in a way that it would no longer
include dependencies when installing a package, effectively leading
to broken images and unusable systems.
Fix that by making sure dependencies are still going to be checked.
Also reduce size of struct abstract_pkg as suggested by @jow- while at
it.
Fixes: 1445d333aa ("opkg: bump to git HEAD")
Signed-off-by: Daniel Golle <daniel@makrotopia.org>