regulator: add missing 'static inline' to a helper's stub

The build fails when CONFIG_REGULATOR is not selected because the stub
for regulator_bulk_set_supply_names() is missing the 'static inline'
attribute.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Link: https://lore.kernel.org/r/20190902151332.28058-1-brgl@bgdev.plSigned-off-by: Mark Brown <broonie@kernel.org>

include/linux/regulator/consumer.h

@@ -586,9 +586,10 @@ static inline int regulator_list_voltage(struct regulator *regulator, unsigned s
 	return -EINVAL;
 }
 
-void regulator_bulk_set_supply_names(struct regulator_bulk_data *consumers,
-				     const char *const *supply_names,
-				     unsigned int num_supplies)
+static inline void
+regulator_bulk_set_supply_names(struct regulator_bulk_data *consumers,
+				const char *const *supply_names,
+				unsigned int num_supplies)
 {
 }