x86_64: asm/ptrace.h needs linux/compiler.h

On x86_64, <asm/ptrace.h> uses __user but doesn't include
<linux/compiler.h>.  This could lead to build failures.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/asm-x86_64/ptrace.h

 #ifndef _X86_64_PTRACE_H
 #define _X86_64_PTRACE_H
 
+#include <linux/compiler.h>	/* For __user */
 #include <asm/ptrace-abi.h>
 
 #ifndef __ASSEMBLY__