global: Convert simple_strtoul() with decimal to dectoul()

It is a pain to have to specify the value 10 in each call. Add a new
dectoul() function and update the code to use it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/pinctrl/pinctrl-uclass.c b/drivers/pinctrl/pinctrl-uclass.c
index ea7275c..dfe60b6 100644
--- a/drivers/pinctrl/pinctrl-uclass.c
+++ b/drivers/pinctrl/pinctrl-uclass.c
@@ -69,7 +69,7 @@
 		 * If statename is not found in "pinctrl-names",
 		 * assume statename is just the integer state ID.
 		 */
-		state = simple_strtoul(statename, &end, 10);
+		state = dectoul(statename, &end);
 		if (*end)
 			return -EINVAL;
 	}