package/faad2: add hash

Upstream do not host the files, they are hosted on SourceForge; SF has
both sha1 and md5, so use the sha1.

Also add a strong, locally computed hash.

Should fix build failures for which sourceforge sends garbage:
    http://autobuild.buildroot.org/results/f0a/f0a36c78fd910bc0aea54df4b76ab8a0f82f7ae4/
    http://autobuild.buildroot.org/results/3d6/3d6134c71e57238d4d865040eac9f34e2d17844c/
    http://autobuild.buildroot.org/results/232/2323f72f9b08ef8e20ec67a5aebfadd5b469a298/


    ...

[Peter: use correct sha1, add link to upstream page listing it]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>