drm: add PCI requirements to low-level drivers.

Now that highlevel DRM no longer requires PCI, we can move the requirement
into the lowlevel drivers.

Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/nouveau/Kconfig b/drivers/gpu/drm/nouveau/Kconfig
index 1175429..b6f5239 100644
--- a/drivers/gpu/drm/nouveau/Kconfig
+++ b/drivers/gpu/drm/nouveau/Kconfig
@@ -1,6 +1,6 @@
 config DRM_NOUVEAU
 	tristate "Nouveau (nVidia) cards"
-	depends on DRM
+	depends on DRM && PCI
         select FW_LOADER
 	select DRM_KMS_HELPER
 	select DRM_TTM