x86, um: get rid of header symlinks

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/um/sys-i386/shared/sysdep/barrier.h

@@ -0,0 +1,9 @@
+#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