perf tools: Drop prefetch.h

This was needed at the time before e66eed651fd1 ("list: remove
prefetching from regular list iterators") where the list iterators did
prefetch elements. This turned out to be counter-productive and hurt
performance and they were removed. Which makes the prefetch.h header
unused so drop it.

Signed-off-by: Borislav Petkov <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Robert Richter <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Makefile.perf

···
 LIB_H += util/include/linux/list.h
 LIB_H += util/include/linux/export.h
 LIB_H += util/include/linux/poison.h
-LIB_H += util/include/linux/prefetch.h
 LIB_H += util/include/linux/rbtree.h
 LIB_H += util/include/linux/rbtree_augmented.h
 LIB_H += util/include/linux/string.h

tools/perf/util/include/linux/list.h

···
 #include <linux/kernel.h>
-#include <linux/prefetch.h>
 
 #include "../../../../include/linux/list.h"
 

tools/perf/util/include/linux/prefetch.h

···
-#ifndef PERF_LINUX_PREFETCH_H
-#define PERF_LINUX_PREFETCH_H
-
-static inline void prefetch(void *a __attribute__((unused))) { }
-
-#endif