package/open2300: switch to github

package/open2300: switch to github

Upstream repository has been dead for quite a while now, and in fact
we are using s.b.o as the "official" location now.

There however exists a Github repository, which is still alive. That
repository has not been touched in a looooong while, but it's still
up, and there is a revision which actually gives the exact same
content (although the hash changes, because the directory name has
changed, from open2300-12/ to open2300-f2198.../).

Also fix spaces in hash file.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>