perf evsel: Add missing 'target' struct forward declaration

We use it in evsel.h but were getting it indirectly, fix it.

Noticed while working on having evsel.h usable by rasd.c.

Cc: Adrian Hunter <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Don Zickus <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Jean Pihet <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

tools/perf/util/evsel.h

@@ -99,6 +99,7 @@ union u64_swap {
 };
 
 struct cpu_map;
+struct target;
 struct thread_map;
 struct perf_evlist;
 struct record_opts;