buildroot

libyuv: update homepage link

The original google code link redirects to the libyuv bug tracker. Use libyuv
git repo as a better sort of a homepage.

Cc: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>