gpio: reintroduce devm_get_gpiod_from_child()

We need to keep this API around for the merge window to avoid
nasty build problems in the merges.

Cc: Lee Jones <lee.jones@linaro.org>
Suggested-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

include/linux/gpio/consumer.h

@@ -143,6 +143,16 @@ struct gpio_desc *devm_fwnode_get_index_gpiod_from_child(struct device *dev,
 						struct fwnode_handle *child,
 						enum gpiod_flags flags,
 						const char *label);
+/* FIXME: delete this helper when users are switched over */
+static inline struct gpio_desc *devm_get_gpiod_from_child(struct device *dev,
+			  const char *con_id, struct fwnode_handle *child)
+{
+	return devm_fwnode_get_index_gpiod_from_child(dev, con_id,
+						      0, child,
+						      GPIOD_ASIS,
+						      "?");
+}
+
 #else /* CONFIG_GPIOLIB */
 
 static inline int gpiod_count(struct device *dev, const char *con_id)
@@ -434,6 +444,13 @@ struct gpio_desc *devm_fwnode_get_index_gpiod_from_child(struct device *dev,
 	return ERR_PTR(-ENOSYS);
 }
 
+/* FIXME: delete this when all users are switched over */
+static inline struct gpio_desc *devm_get_gpiod_from_child(struct device *dev,
+			  const char *con_id, struct fwnode_handle *child)
+{
+	return ERR_PTR(-ENOSYS);
+}
+
 #endif /* CONFIG_GPIOLIB */
 
 static inline