opkg: upgrade to version 0.6.1

opkg: upgrade to version 0.6.1

Opkg 0.6.1 Changes:
- Opkg will no longer complain when trying to clean up the temporary
  directory, if the directory does not exist.
- Fixed a SEGFAULT when parsing package indexes with invalid `Size` or
  `Installed-Size` fields. These indexes will now produce a
  comprehensible error.
- Fixed an inconsistecy in .list generation where files would sometimes
  be entered with/without a trailing slash. The trailng slash should now
  always be removed.
- Fixed [a bug](https://bugzilla.yoctoproject.org/show_bug.cgi?id=10461)
  in package removal, where empty common directories would be left on
  disk, even after all owning packages were removed.

Signed-off-by: Alex Stewart <alex.stewart@ni.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>