x86/um: reuse asm-generic/barrier.h

commit 577f183a upstream.

On x86/um CONFIG_SMP is never defined.  As a result, several macros
match the asm-generic variant exactly. Drop the local definitions and
pull in asm-generic/barrier.h instead.

This is in preparation to refactoring this code area.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Richard Weinberger <richard@nod.at>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

arch/x86/um/asm/barrier.h

@@ -51,11 +51,7 @@
 
 #else /* CONFIG_SMP */
 
-#define smp_mb()	barrier()
-#define smp_rmb()	barrier()
-#define smp_wmb()	barrier()
-#define smp_read_barrier_depends()	do { } while (0)
-#define set_mb(var, value) do { var = value; barrier(); } while (0)
+#include <asm-generic/barrier.h>
 
 #endif /* CONFIG_SMP */