percpu: remove this_cpu_xor() implementation

There is not a single user in the whole kernel.
Besides that this_cpu_xor() is broken anyway since it gets
translated to this_cpu_or() (see __pcpu_size_call() line).

So instead of fixing an unused definition just remove it.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

include/linux/percpu.h

@@ -375,22 +375,6 @@ do {									\
 # define this_cpu_or(pcp, val)		__pcpu_size_call(this_cpu_or_, (pcp), (val))
 #endif
 
-#ifndef this_cpu_xor
-# ifndef this_cpu_xor_1
-#  define this_cpu_xor_1(pcp, val)	_this_cpu_generic_to_op((pcp), (val), ^=)
-# endif
-# ifndef this_cpu_xor_2
-#  define this_cpu_xor_2(pcp, val)	_this_cpu_generic_to_op((pcp), (val), ^=)
-# endif
-# ifndef this_cpu_xor_4
-#  define this_cpu_xor_4(pcp, val)	_this_cpu_generic_to_op((pcp), (val), ^=)
-# endif
-# ifndef this_cpu_xor_8
-#  define this_cpu_xor_8(pcp, val)	_this_cpu_generic_to_op((pcp), (val), ^=)
-# endif
-# define this_cpu_xor(pcp, val)		__pcpu_size_call(this_cpu_or_, (pcp), (val))
-#endif
-
 #define _this_cpu_generic_add_return(pcp, val)				\
 ({									\
 	typeof(pcp) ret__;						\
@@ -629,22 +613,6 @@ do {									\
 # define __this_cpu_or(pcp, val)	__pcpu_size_call(__this_cpu_or_, (pcp), (val))
 #endif
 
-#ifndef __this_cpu_xor
-# ifndef __this_cpu_xor_1
-#  define __this_cpu_xor_1(pcp, val)	__this_cpu_generic_to_op((pcp), (val), ^=)
-# endif
-# ifndef __this_cpu_xor_2
-#  define __this_cpu_xor_2(pcp, val)	__this_cpu_generic_to_op((pcp), (val), ^=)
-# endif
-# ifndef __this_cpu_xor_4
-#  define __this_cpu_xor_4(pcp, val)	__this_cpu_generic_to_op((pcp), (val), ^=)
-# endif
-# ifndef __this_cpu_xor_8
-#  define __this_cpu_xor_8(pcp, val)	__this_cpu_generic_to_op((pcp), (val), ^=)
-# endif
-# define __this_cpu_xor(pcp, val)	__pcpu_size_call(__this_cpu_xor_, (pcp), (val))
-#endif
-
 #define __this_cpu_generic_add_return(pcp, val)				\
 ({									\
 	__this_cpu_add(pcp, val);					\