cpu/intel/model_67x: Add missing include

The added device.h file was indirectly picked from cpu.h, which will
have this include removed in a follow-up patch.

Change-Id: Ifc0a4800de3b1ef220ab1034934f583be8c527b0
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/3826
Tested-by: build bot (Jenkins)

src/cpu/intel/model_67x/model_67x_init.c

@@ -20,6 +20,7 @@
 
 #include <console/console.h>
 #include <string.h>
+#include <device/device.h>
 #include <cpu/cpu.h>
 #include <cpu/x86/mtrr.h>
 #include <cpu/x86/lapic.h>