drm: Fix support for PCI domains

(For some reason I thought that went in ages ago ...)

This fixes support for PCI domains in what should hopefully be a backward
compatible way along with a change to libdrm.

When the interface version is set to 1.4, we assume userspace understands
domains and the world is at peace. We thus pass proper domain numbers
instead of 0 to userspace.

The newer libdrm will then try 1.4 first, and fallback to 1.1, along with
ignoring domains in the later case (well, except on alpha of course)

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 7b03b19..47db4df 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -392,6 +392,7 @@
 		if (sv->drm_di_minor >= 1) {
 			/*
 			 * Version 1.1 includes tying of DRM to specific device
+			 * Version 1.4 has proper PCI domain support
 			 */
 			retcode = drm_set_busid(dev, file_priv);
 			if (retcode)