regulator: fix kernel-doc warning in consumer.h

Fix kernel-doc warning about internal/private data by marking it
as "private:" so that kernel-doc will ignore it.

  Warning(include/linux/regulator/consumer.h:128): No description found for parameter 'ret'
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/regulator/consumer.h

@@ -123,7 +123,7 @@ struct regulator_bulk_data {
 	const char *supply;
 	struct regulator *consumer;
 
-	/* Internal use */
+	/* private: Internal use */
 	int ret;
 };