OPP: Populate required opp tables from "required-opps" property

The current implementation works only for the case where a single
phandle is present in the "required-opps" property, while DT allows
multiple phandles to be present there.

This patch adds new infrastructure to parse all the phandles present in
"required-opps" property and save pointers of the required OPP's OPP
tables. These will be used by later commits.

Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
diff --git a/drivers/opp/opp.h b/drivers/opp/opp.h
index cdb0c2b..024e1be 100644
--- a/drivers/opp/opp.h
+++ b/drivers/opp/opp.h
@@ -133,6 +133,9 @@ enum opp_table_access {
  * @parsed_static_opps: True if OPPs are initialized from DT.
  * @shared_opp: OPP is shared between multiple devices.
  * @suspend_opp: Pointer to OPP to be used during device suspend.
+ * @required_opp_tables: List of device OPP tables that are required by OPPs in
+ *		this table.
+ * @required_opp_count: Number of required devices.
  * @supported_hw: Array of version number to support.
  * @supported_hw_count: Number of elements in supported_hw array.
  * @prop_name: A name to postfix to many DT properties, while parsing them.
@@ -172,6 +175,9 @@ struct opp_table {
 	enum opp_table_access shared_opp;
 	struct dev_pm_opp *suspend_opp;
 
+	struct opp_table **required_opp_tables;
+	unsigned int required_opp_count;
+
 	unsigned int *supported_hw;
 	unsigned int supported_hw_count;
 	const char *prop_name;
@@ -208,9 +214,11 @@ void _put_opp_list_kref(struct opp_table *opp_table);
 
 #ifdef CONFIG_OF
 void _of_init_opp_table(struct opp_table *opp_table, struct device *dev, int index);
+void _of_clear_opp_table(struct opp_table *opp_table);
 struct opp_table *_managed_opp(struct device *dev, int index);
 #else
 static inline void _of_init_opp_table(struct opp_table *opp_table, struct device *dev, int index) {}
+static inline void _of_clear_opp_table(struct opp_table *opp_table) {}
 static inline struct opp_table *_managed_opp(struct device *dev, int index) { return NULL; }
 #endif