drm/nve0/fifo: allocate usermem as needed

Memory was always allocated for 4096 channels. Change this to allocate
what we actually need according to the number of channels we use.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/core/engine/fifo/nve0.c

@@ -852,8 +852,8 @@ nve0_fifo_ctor(struct nouveau_object *parent, struct nouveau_object *engine,
 			return ret;
 	}
 
-	ret = nouveau_gpuobj_new(nv_object(priv), NULL, 4096 * 0x200, 0x1000,
-				 NVOBJ_FLAG_ZERO_ALLOC, &priv->user.mem);
+	ret = nouveau_gpuobj_new(nv_object(priv), NULL, impl->channels * 0x200,
+				0x1000, NVOBJ_FLAG_ZERO_ALLOC, &priv->user.mem);
 	if (ret)
 		return ret;