drm/nouveau: use the correct fence implementation for nv50

Only compile time tested, noticed nv50_fence_create was never used,
so fix this. This will probably fix vblank on nv50 cards.

Hopefully this is still in time for 3.7 final release.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_drm.c

@@ -129,7 +129,8 @@ nouveau_accel_init(struct nouveau_drm *drm)
 
 	/* initialise synchronisation routines */
 	if      (device->card_type < NV_10) ret = nv04_fence_create(drm);
-	else if (device->chipset   <  0x84) ret = nv10_fence_create(drm);
+	else if (device->card_type < NV_50) ret = nv10_fence_create(drm);
+	else if (device->chipset   <  0x84) ret = nv50_fence_create(drm);
 	else if (device->card_type < NV_C0) ret = nv84_fence_create(drm);
 	else                                ret = nvc0_fence_create(drm);
 	if (ret) {