mlxsw: spectrum_router: Fix an IS_ERR() vs NULL check

The mlxsw_sp_crif_alloc() function returns NULL on error.  It doesn't
return error pointers.  Fix the check.

Fixes: 78126cf ("mlxsw: spectrum_router: Maintain CRIF for fallback loopback RIF")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Dan Carpenter

drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c

@@ -10794,8 +10794,8 @@ static int mlxsw_sp_lb_rif_init(struct mlxsw_sp *mlxsw_sp,
 	int err;
 
 	router->lb_crif = mlxsw_sp_crif_alloc(NULL);
-	if (IS_ERR(router->lb_crif))
-		return PTR_ERR(router->lb_crif);
+	if (!router->lb_crif)
+		return -ENOMEM;
 
 	/* Create a generic loopback RIF associated with the main table
 	 * (default VRF). Any table can be used, but the main table exists