drm: Remove pci_vendor and pci_device from struct drm_device

We can get the PCI vendor and device IDs via dev->pdev. So we can drop
the duplicated information.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>