gpio: stm32_gpio: do not mix error code types

Change-Id: I84f8a99be2dcdf7c51fbecdb324df8e2f32cc855
Signed-off-by: Nicolas Le Bayon <nicolas.le.bayon@st.com>
Signed-off-by: Yann Gautier <yann.gautier@st.com>

drivers/st/gpio/stm32_gpio.c

@@ -165,7 +165,7 @@ int dt_set_pinctrl_config(int node)
 	void *fdt;
 
 	if (fdt_get_address(&fdt) == 0) {
-		return -ENOENT;
+		return -FDT_ERR_NOTFOUND;
 	}
 
 	if (status == DT_DISABLED) {