tools: Fix shadowed declaration in err.h

The error variable breaks build on CentOS 6.7, due to collision with
global error symbol:

    CC       util/evlist.o
  cc1: warnings being treated as errors
  In file included from util/evlist.c:28:
  tools/include/linux/err.h: In function ‘ERR_PTR’:
  tools/include/linux/err.h:34: error: declaration of ‘error’ shadows a global declaration
  util/util.h:135: error: shadowed declaration is here

Using 'error_' name instead to fix it.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/n/tip-i9mdgdbrgauy3fe76s9rd125@git.kernel.orgReported-by: Vinson Lee <vlee@twopensource.com>
[ Use 'error_' instead of 'err' to, visually, not diverge too much from include/linux/err.h ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/include/linux/err.h

@@ -31,9 +31,9 @@
 
 #define IS_ERR_VALUE(x) unlikely((x) >= (unsigned long)-MAX_ERRNO)
 
-static inline void * __must_check ERR_PTR(long error)
+static inline void * __must_check ERR_PTR(long error_)
 {
-	return (void *) error;
+	return (void *) error_;
 }
 
 static inline long __must_check PTR_ERR(__force const void *ptr)