perf tools: Add missing forward declaration of struct map to probe-event.h

perf tools: Add missing forward declaration of struct map to probe-event.h

Commit 7b6ff0bdbf4f7f429c2116cca92a6d171217449e ("perf probe ppc64le:
Fixup function entry if using kallsyms lookup") adds 'struct map' into
probe-event.h but not forward declares it. This patch fixes it.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kaixu Xia <xiakaixu@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Fixes: 7b6ff0bdbf4f ("perf probe ppc64le: Fixup function entry if using kallsyms lookup")
Link: http://lkml.kernel.org/n/1436445342-1402-30-git-send-email-wangnan0@huawei.com
[ No need to include map.h, just forward declare 'struct map' ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>