pinctrl: stm32: return proper error code in pin_config_set

".pin_config_set" or ".pin_config_group_set" can be called with a
configuration not supported (i.e. PIN_CONFIG_PERSIST_STATE). In this case,
it is more suitable to return -ENOTSUPP instead of -EINVAL.
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>
Link: https://lore.kernel.org/r/20200615125951.28008-2-alexandre.torgue@st.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/stm32/pinctrl-stm32.c

@@ -1085,7 +1085,7 @@ static int stm32_pconf_parse_conf(struct pinctrl_dev *pctldev,
 		ret = stm32_pmx_gpio_set_direction(pctldev, range, pin, false);
 		break;
 	default:
-		ret = -EINVAL;
+		ret = -ENOTSUPP;
 	}
 
 	return ret;