perf tests: Take into account address of each objdump line

objdump output can contain repeated bytes. At the moment test reads all
output sequentially, assuming each address is represented in output only
once:

  ffffffff8164efb3 <retint_swapgs+0x9>:
  ffffffff8164efb3:  c1 5d 00 eb        rcrl   $0xeb,0x0(%rbp)
  ffffffff8164efb7:  00 4c 8b 5c        add    %cl,0x5c(%rbx,%rcx,4)

  ffffffff8164efb8 <restore_c_regs_and_iret>:
  ffffffff8164efb8:  4c 8b 5c 24 30     mov    0x30(%rsp),%r11
  ffffffff8164efbd:  4c 8b 54 24 38     mov    0x38(%rsp),%r10

Store objdump output to buffer according to offset calculated from
address on each line.

Signed-off-by: Jan Stancek <jstancek@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/ad13289a55d6350f7717757c7e32c2d4286402bd.1441181335.git.jstancek@redhat.com


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