drm/nouveu: fix swiotlb include

The check for swiotlb has moved to nouveu_ttm.c, but we forgot to move
the include as well.

This blows up only when merged with linux-next, not sure why drm-misc-next
works stand alone.
Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/397835/

drivers/gpu/drm/nouveau/nouveau_bo.c

@@ -28,7 +28,6 @@
  */
 
 #include <linux/dma-mapping.h>
-#include <linux/swiotlb.h>
 
 #include "nouveau_drv.h"
 #include "nouveau_chan.h"

drivers/gpu/drm/nouveau/nouveau_ttm.c

@@ -22,6 +22,9 @@
  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  * USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
+
+#include <linux/swiotlb.h>
+
 #include "nouveau_drv.h"
 #include "nouveau_gem.h"
 #include "nouveau_mem.h"