gupnp: remove dependency on gnome-icon-theme

As discussed in [1], let's remove the dependency on gnome-icon-theme,
since it's not required, and it brings additional unwanted dependency,
such as the whole gtk+...

[1] http://article.gmane.org/gmane.comp.handhelds.openembedded/57483



It is build-tested with
 - core-image-minimal
 - IMAGE_INSTALL += 'gupnp'
 - directfb in DISTRO_FEATURES

The build was failing before (GTK failed to build with directfb, which
is expected).

Signed-off-by: Nicolas Dechesne <ndec@linaro.org>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>