perf hists: Print newline between hists callchains

Tiny cosmetic fix. The lack of a newline between hists callchains was
looking slightly messy.

Before:

     0.24%      swapper  [kernel.kallsyms]  [k] _raw_spin_lock_irq
                |
                --- _raw_spin_lock_irq
                    run_timer_softirq
                    __do_softirq
                    call_softirq
                    do_softirq
                    irq_exit
                    smp_apic_timer_interrupt
                    apic_timer_interrupt
                    default_idle
                    amd_e400_idle
                    cpu_idle
                    start_secondary
     0.10%         perf  [kernel.kallsyms]  [k] lock_is_held
                   |
                   --- lock_is_held
                       __might_sleep
                       mutex_lock_nested
                       perf_event_for_each_child
                       perf_ioctl
                       do_vfs_ioctl
                       sys_ioctl
                       system_call_fastpath
                       ioctl
                       cmd_record
                       run_builtin
                       main
                       __libc_start_main

After:

     0.24%      swapper  [kernel.kallsyms]  [k] _raw_spin_lock_irq
                |
                --- _raw_spin_lock_irq
                    run_timer_softirq
                    __do_softirq
                    call_softirq
                    do_softirq
                    irq_exit
                    smp_apic_timer_interrupt
                    apic_timer_interrupt
                    default_idle
                    amd_e400_idle
                    cpu_idle
                    start_secondary

     0.10%         perf  [kernel.kallsyms]  [k] lock_is_held
                   |
                   --- lock_is_held
                       __might_sleep
                       mutex_lock_nested
                       perf_event_for_each_child
                       perf_ioctl
                       do_vfs_ioctl
                       sys_ioctl
                       system_call_fastpath
                       ioctl
                       cmd_record
                       run_builtin
                       main
                       __libc_start_main
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1342631456-7233-3-git-send-email-fweisbec@gmail.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/hist.c

@@ -749,6 +749,8 @@ static size_t callchain__fprintf_graph(FILE *fp, struct rb_root *root,
 
 	ret += __callchain__fprintf_graph(fp, root, total_samples,
 					  1, 1, left_margin);
+	ret += fprintf(fp, "\n");
+
 	return ret;
 }