cpufreq: schedutil: Remove needless sg_policy parameter from ignore_dl_rate_limit()

Since sg_policy is a member of struct sugov_cpu.

Also remove the local variable in sugov_update_single_common() to
make the code more clean.

Signed-off-by: Yue Hu <huyue2@yulong.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
[ rjw: Minor subject edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>