netbase: update SRC_URI

The upstream oe-core recipe fixed similar fetcher issues by switching
to a specific debian snapshot version. However, the debian snapshot
doesn't provide netbase v5.2 so fetch from yoctoproject.org mirror
instead.

Signed-off-by: Andre McCurdy <armccurdy@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>