In branch mode, the branch symbols were being displayed with incorrect
cpumode labels. So fix this.

For example, before:
  # perf record -b -a -- sleep 1
  # perf report -b

  Overhead  Command  Source Shared Object  Source Symbol               Target Symbol
     0.08%  swapper  [kernel.kallsyms]     [k] rcu_idle_enter          [k] cpuidle_enter_state
 ==> 0.08%  cmd0     [kernel.kallsyms]     [.] psi_group_change        [.] psi_group_change
     0.08%  cmd1     [kernel.kallsyms]     [k] psi_group_change        [k] psi_group_change

After:
  # perf report -b

  Overhead  Command  Source Shared Object  Source Symbol               Target Symbol
     0.08%  swapper  [kernel.kallsyms]     [k] rcu_idle_enter          [k] cpuidle_enter_state
     0.08%  cmd0     [kernel.kallsyms]     [k] psi_group_change        [k] pei_group_change
     0.08%  cmd1     [kernel.kallsyms]     [k] psi_group_change        [k] psi_group_change
Reviewed-by: James Clark <james.clark@arm.com>
Signed-off-by: German Gomez <german.gomez@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20220126105927.3411216-1-german.gomez@arm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>