This matches the existing behavior in arch/tile/Makefile for defconfig.

Reported-by: fengguang.wu@intel.com
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NTony Lu <zlu@tilera.com>
Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>