commonlib/clamp.h: Relicense file to be BSD-compatible

I added this header in commit a6c8b4becb
(nb/intel/sandybridge: Rewrite get_FRQ). Relicense it as "BSD-3-Clause
OR GPL-2.0-or-later" and move it into the BSD-licensed commonlib part.

Change-Id: I89ebdcdf8d06e78e624e37a443696981b3b17b7d
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/66711
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/commonlib/bsd/include/commonlib/bsd/clamp.h

@@ -1,7 +1,7 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
+/* SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0-or-later */
 
-#ifndef COMMONLIB_CLAMP_H
-#define COMMONLIB_CLAMP_H
+#ifndef COMMONLIB_BSD_CLAMP_H
+#define COMMONLIB_BSD_CLAMP_H
 
 #include <stdint.h>
 
@@ -19,4 +19,4 @@ static inline u32 clamp_u32(const u32 min, const u32 val, const u32 max)
 	return val;
 }
 
-#endif /* COMMONLIB_CLAMP_H */
+#endif /* COMMONLIB_BSD_CLAMP_H */