package/valgrind: bump version to 3.21.0
Added sha1 hash provided by upstream, removed md5 hash.
Release notes: https://valgrind.org/docs/manual/dist.news.html
Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>