cpufreq: ondemand: fix wrong delay sampling rate

Restore the correct delay value for ondemand's od_dbs_timer, as it was
changed erroneously in commit 83f0e55 (cpufreq: governors: remove
redundant code).

Signed-off-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>