c6x: use asm-generic/barrier.h

A recent patch in the linux-next tree caused a build failure on
C6X because C6X didn't define a read_barrier_depends() macro. C6X
does not support SMP and the architecture doesn't provide any
special memory ordering instructions, so it makes sense to just
use the generic barrier.h rather than patching the existing c6x
specific header.
Signed-off-by: Mark Salter <msalter@redhat.com>

arch/c6x/include/asm/Kbuild

@@ -2,6 +2,7 @@ include include/asm-generic/Kbuild.asm
 
 generic-y += atomic.h
 generic-y += auxvec.h
+generic-y += barrier.h
 generic-y += bitsperlong.h
 generic-y += bugs.h
 generic-y += cputime.h

arch/c6x/include/asm/barrier.h

-/*
- *  Port on Texas Instruments TMS320C6x architecture
- *
- *  Copyright (C) 2004, 2009, 2010, 2011 Texas Instruments Incorporated
- *  Author: Aurelien Jacquiot (aurelien.jacquiot@jaluna.com)
- *
- *  This program is free software; you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License version 2 as
- *  published by the Free Software Foundation.
- */
-#ifndef _ASM_C6X_BARRIER_H
-#define _ASM_C6X_BARRIER_H
-
-#define nop()                    asm("NOP\n");
-
-#define mb()                     barrier()
-#define rmb()                    barrier()
-#define wmb()                    barrier()
-#define set_mb(var, value)       do { var = value;  mb(); } while (0)
-#define set_wmb(var, value)      do { var = value; wmb(); } while (0)
-
-#define smp_mb()	         barrier()
-#define smp_rmb()	         barrier()
-#define smp_wmb()	         barrier()
-#define smp_read_barrier_depends()	do { } while (0)
-
-#endif /* _ASM_C6X_BARRIER_H */