php-geoip: get tarball from sources.buildroot.net

pecl.php.net seems to have a database issue and returns a html page instead
of the tarball.

Fixes http://autobuild.buildroot.net/results/c56/c56b3bf6c141b2b9b9062816bec559b2529534a1/



Signed-off-by: Peter Korsgaard <peter@korsgaard.com>