CPU/intel: Add missing license headers

Add missing license headers to files that have no coreboot header.

Change-Id: Iaaa04b5dcbd446a2064ac68d501ae8e860486e36
Signed-off-by: Damien Roth <yves.r.roth@gmail.com>
Reviewed-on: https://review.coreboot.org/13289
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

src/cpu/intel/hyperthreading/intel_sibling.c

@@ -1,3 +1,16 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
 #include <console/console.h>
 #include <cpu/cpu.h>
 #include <cpu/x86/lapic.h>