twl4030_charger: add missing iio dependency

This driver fails to link without CONFIG_IIO, since
there are no stubs for the iio_channels functions.
Signed-off-by: Sebastian Reichel <sre@kernel.org>
Acked-by: Marek Belisko <marek@goldelico.com>
Acked-by: Nikolaus Schaller <hns@goldelico.com>

drivers/power/Kconfig

@@ -313,7 +313,7 @@ config CHARGER_MAX8903
 
 config CHARGER_TWL4030
 	tristate "OMAP TWL4030 BCI charger driver"
-	depends on TWL4030_CORE
+	depends on IIO && TWL4030_CORE
 	help
 	  Say Y here to enable support for TWL4030 Battery Charge Interface.