pinctrl/abx500: replace incorrect return value

Currently in the empty abx500_pin_config_get() function, we're
returning -EINVAL, with a comment stating that the reason for the
failure is that the function isn't implemented yet. Well there's
a proper return code for that. If we use it, we can do away with
the comment too, as it would be implied.
Signed-off-by: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/pinctrl-abx500.c

@@ -971,8 +971,7 @@ int abx500_pin_config_get(struct pinctrl_dev *pctldev,
 		       unsigned pin,
 		       unsigned long *config)
 {
-	/* Not implemented */
-	return -EINVAL;
+	return -ENOSYS;
 }
 
 int abx500_pin_config_set(struct pinctrl_dev *pctldev,