perf annotate: Don't try to follow jump target on PLT symbols

The perf annotate browser on TUI can identify a jump target for a
selected instruction.  It assumes that the jump target is within the
function but it's not the case of PLT symbols which have offset out of
the function as a target.

Since it caused a segmentation fault, do not try to follow jump target
on the PLT symbols.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1352482044-3443-5-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>