gstreamer1.0-plugins-good: Fix libsoup runtime dependency

The runtime dependency on libsoup set via PACKAGECONFIG does not work.
The problem is the dependency is placed on the main package, but the
soup package has no dependency on the main package.

I considered modifying the call to do_split_packages from
gstreamer1.0-plugins-packaging.inc, changing extra_depends from '' to
None:

```
    extra_depends  -- extra runtime dependencies (RDEPENDS) to be set for
                      all packages. The default value of None causes a
                      dependency on the main package (${PN}) - if you do
                      not want this, pass '' for this parameter.
```

However, the problem with this solution is that it does add the runtime
dependency to _all_ such split packages.

So, fix the problem with an explicit runtime dependency.

Signed-off-by: Tom Hochstein <tom.hochstein@nxp.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>