perf ppc64le: Fix build failure when libelf is not present

arch__post_process_probe_trace_events() calls get_target_map() to
prepare symbol table. get_target_map() is defined inside
util/probe-event.c.

probe-event.c will only get included in perf binary if CONFIG_LIBELF is
set.  Hence arch__post_process_probe_trace_events() needs to be defined
inside #ifdef HAVE_LIBELF_SUPPORT to solve compilation error.

Reported-and-Tested-by: Anton Blanchard <anton@samba.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/57ABFF88.8030905@linux.vnet.ibm.com


[ Thunderbird MUA mangled it, fix that ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>