um: sysdep/barrier.h is not used for anything

Signed-off-by: Al Viro <[e-mail]>
Signed-off-by: Richard Weinberger <[e-mail]>

arch/um/os-Linux/signal.c

···
 #include "as-layout.h"
 #include "kern_util.h"
 #include "os.h"
-#include "sysdep/barrier.h"
 #include "sysdep/mcontext.h"
 
 void (*sig_info[NSIG])(int, struct uml_pt_regs *) = {

arch/um/sys-x86/shared/sysdep/barrier.h

···
-#ifdef __i386__
-#include "barrier_32.h"
-#else
-#include "barrier_64.h"
-#endif

arch/um/sys-x86/shared/sysdep/barrier_32.h

···
-#ifndef __SYSDEP_I386_BARRIER_H
-#define __SYSDEP_I386_BARRIER_H
-
-/* Copied from include/asm-i386 for use by userspace.  i386 has the option
- * of using mfence, but I'm just using this, which works everywhere, for now.
- */
-#define mb() asm volatile("lock; addl $0,0(%esp)")
-
-#endif

arch/um/sys-x86/shared/sysdep/barrier_64.h

···
-#ifndef __SYSDEP_X86_64_BARRIER_H
-#define __SYSDEP_X86_64_BARRIER_H
-
-/* Copied from include/asm-x86_64 for use by userspace. */
-#define mb() 	asm volatile("mfence":::"memory")
-
-#endif