power_supply: Add core support for supplied_from

This patch adds support for supplies to register a list of char *'s which
represent the list of supplies which supply them. This is the opposite as
the supplied_to list.

This change maintains support for supplied_to until all drivers which make
use of it already are converted.

Signed-off-by: Rhyland Klein <rklein@nvidia.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Anton Vorontsov <anton@enomsg.org>
diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
index 002a99f..c1cbd5e 100644
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -171,6 +171,9 @@
 	char **supplied_to;
 	size_t num_supplicants;
 
+	char **supplied_from;
+	size_t num_supplies;
+
 	int (*get_property)(struct power_supply *psy,
 			    enum power_supply_property psp,
 			    union power_supply_propval *val);