perf tools: Fix missing top level callchain

While recursively printing the branches of each callchains, we
forget to display the root. It is never printed.

Say we have:

    symbol
    f1
    f2
     |
     -------- f3
     |        f4
     |
     ---------f5
              f6

Actually we never see that, instead it displays:

    symbol
    |
    --------- f3
    |         f4
    |
    --------- f5
              f6

However f1 is always the same than "symbol" and if we are
sorting by symbols first then "symbol", f1 and f2 will be well
aligned like in the above example, so displaying f1 looks
redundant here.

But if we are sorting by something else first (dso, comm,
etc...), displaying f1 doesn't look redundant but rather
necessary because the symbol is not well aligned anymore with
its callchain:

     comm     dso        symbol
     f1
     f2
     |
     --------- [...]

And we want the callchain to be obvious.
So we fix the bug by printing the root branch, but we also
filter its first entry if we are sorting by symbols first.

Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1256246604-17156-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>