iris: Use Mesa internal drm-uapi headers

Iris driver includes system DRM UAPI header before the Mesa's internal
ones, which makes Iris to use the system headers. Correct the included
header for consistency with the rest of the Intel driver code by changing
the inclusion order, like it's done by the rest of the Intel driver code.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27043>

src/gallium/drivers/iris/iris_bufmgr.c

@@ -31,7 +31,6 @@
  * - main interface to GEM in the kernel
  */
 
-#include <xf86drm.h>
 #include <util/u_atomic.h>
 #include <fcntl.h>
 #include <stdio.h>
@@ -72,6 +71,7 @@
 #include "xe/iris_bufmgr.h"
 
 #include "drm-uapi/i915_drm.h"
+#include <xf86drm.h>
 
 #ifdef HAVE_VALGRIND
 #include <valgrind.h>