nios2: remove wrapper header for cmpxchg.h

Since commit 713e9b80 ("nios2: Switch to generic __xchg()")
asm/cmpxchg.h for nios2 is merely including asm-generic/cmpxchg.h. Thus,
the wrapper can be omitted and the generic header can be used directly.
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Acked-by: Ley Foon Tan <ley.foon.tan@intel.com>

arch/nios2/include/asm/Kbuild

@@ -6,6 +6,7 @@ generic-y += bitsperlong.h
 generic-y += bug.h
 generic-y += bugs.h
 generic-y += clkdev.h
+generic-y += cmpxchg.h
 generic-y += current.h
 generic-y += device.h
 generic-y += div64.h

arch/nios2/include/asm/cmpxchg.h

-/*
- * Copyright (C) 2004 Microtronix Datacom Ltd.
- *
- * This file is subject to the terms and conditions of the GNU General Public
- * License. See the file "COPYING" in the main directory of this archive
- * for more details.
- */
-
-#ifndef _ASM_NIOS2_CMPXCHG_H
-#define _ASM_NIOS2_CMPXCHG_H
-
-#include <asm-generic/cmpxchg.h>
-
-#endif /* _ASM_NIOS2_CMPXCHG_H */