perf symbols: Fix a memory leak due to symbol__delete not being used

In function symbols__fixup_duplicate(), while duplicated symbols are
found, only the rb_node is removed from the tree. The symbol structures
themself are ignored.  Then, these memory areas are lost.

Signed-off-by: Chenggang Qin <chenggang.qcg@taobao.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Yanmin Zhang <yanmin.zhang@intel.com>
Link: http://lkml.kernel.org/r/1381451279-4109-3-git-send-email-chenggang.qin@gmail.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>