OPP: Remove unused declarations in header file

The definition of _update_set_required_opps() has been removed since
commit e37440e ("OPP: Call dev_pm_opp_set_opp() for required
OPPs").

Besides, the definition of _put_opp_list_kref() has been removed since
commit 03758d6 ("opp: Replace list_kref with a local counter").
Let's remove the empty declarations in header file.

Signed-off-by: Zhang Zekun <zhangzekun11@huawei.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/opp/opp.h

@@ -262,9 +262,7 @@ int _opp_add(struct device *dev, struct dev_pm_opp *new_opp, struct opp_table *o
 int _opp_add_v1(struct opp_table *opp_table, struct device *dev, struct dev_pm_opp_data *data, bool dynamic);
 void _dev_pm_opp_cpumask_remove_table(const struct cpumask *cpumask, int last_cpu);
 struct opp_table *_add_opp_table_indexed(struct device *dev, int index, bool getclk);
-void _put_opp_list_kref(struct opp_table *opp_table);
 void _required_opps_available(struct dev_pm_opp *opp, int count);
-void _update_set_required_opps(struct opp_table *opp_table);
 
 static inline bool lazy_linking_pending(struct opp_table *opp_table)
 {