Test soc path for modalias needed by drm

Test soc path for modalias needed by drm

On ARM, both pci and soc path can be tested for drm.

With this patchset, that was missing in recent kernel,
the tegra_drm case is not needed anymore:
http://patchwork.ozlabs.org/patch/361765/
http://www.spinics.net/lists/linux-tegra/msg17948.html