cpufreq: stats: Do not stop notification call chain
The notification call chain is stopped if error returned. Since
no further steps is needed to handle such error, let is just print
a debug message here so the other registered cpufreq notifier can
be called correctly.

Signed-off-by: Lianwei Wang <a22439@motorola.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>