buildroot

yaml-cpp: Bump version and change site

Google Code is a closing forge, yaml-cpp has already made the move
to Github.

Since a new release was available a bump was also in order.
The hash is removed since the tarball from Github is generated.

Signed-off-by: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>