perf tools powerpc: Use dwfl_report_elf() instead of offline.

dwfl_report_offline() works only when libraries are prelinked.

Replace dwfl_report_offline() with dwfl_report_elf() so we correctly
extract debug info even from libraries that are not prelinked.

Reported-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Tested-by: Jiri Olsa <jolsa@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Link: http://lkml.kernel.org/r/20150114221045.GA17703@us.ibm.com


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