perf rblist: Create rblist__exit() function

perf rblist: Create rblist__exit() function

Currently we have a rblist__delete() which is used to delete a rblist.
While rblist__delete() will free the pointer of rblist at the end.

It's an inconvenience for the user to delete a rblist which is not
allocated by something like malloc(). For example, the rblist is
embedded in a larger data structure.

This patch creates a new function rblist__exit() which is similar to
rblist__delete() but it will not free the pointer of rblist.

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1512125856-22056-2-git-send-email-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>