cpufreq: conservative: Simplify the condition of storing 'down_threshold'

The governor currently checks if the input new down_threshold is less
than 100 before storing it, but the up_threshold field of dbs_data
structure is also limited to be less than 100, so this check is
unnecessary and remove it.

Signed-off-by: Liao Chang <liaochang1@huawei.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>