[legal] Add missing FILE_LICENCE declarations

Add missing FILE_LICENCE declarations to x86_64 headers based on the
corresponding i386 headers (from which the x86_64 headers were
originally derived).

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/x86_64/include/bits/compiler.h

 #ifndef _BITS_COMPILER_H
 #define _BITS_COMPILER_H
 
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
 /** Dummy relocation type */
 #define RELOC_TYPE_NONE R_X86_64_NONE
 

src/arch/x86_64/include/bits/stdint.h

 #ifndef _BITS_STDINT_H
 #define _BITS_STDINT_H
 
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
 typedef __SIZE_TYPE__		size_t;
 typedef signed long		ssize_t;
 typedef signed long		off_t;

src/arch/x86_64/include/limits.h

 #ifndef LIMITS_H
 #define LIMITS_H	1
 
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
 /* Number of bits in a `char' */
 #define CHAR_BIT	8