extcon: Fix return value in extcon_register_interest()

Propagate the value returned from extcon_find_cable_index()
instead of -ENODEV. For readability, -EINVAL is returned in place of
the variable.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>

drivers/extcon/extcon-class.c

@@ -469,7 +469,7 @@ int extcon_register_interest(struct extcon_specific_cable_nb *obj,
 
 	obj->cable_index = extcon_find_cable_index(obj->edev, cable_name);
 	if (obj->cable_index < 0)
-		return -ENODEV;
+		return -EINVAL;
 
 	obj->user_nb = nb;