cpufreq: governor: Rename skip_work to work_count

The skip_work field in struct policy_dbs_info technically is a
counter, so give it a new name to reflect that.

No functional changes.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>