package/open2300: add hash file

package/open2300: add hash file

Add sha245 hashes for the source taball and the license file.

Note: the upstream subversion tree for open2300 is off-line (and the
package is no longer maintained), so the tarball is retrieved from
sources.buildroot.org, which makes it a stable (reproducible) tarball,
when our svn backend is in fact not stable.

Signed-off-by: Heiko Thiery <heiko.thiery@gmail.com>
[yann.morin.1998@free.fr:
  - add the comment in the .hash file
  - update the commit log accordingly
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>