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>

include/vsprintf.h

@@ -37,6 +37,19 @@ ulong simple_strtoul(const char *cp, char **endp, unsigned int base);
  */
 unsigned long hextoul(const char *cp, char **endp);
 
+/**
+ * dec_strtoul - convert a string in decimal to an unsigned long
+ *
+ * @param cp	The string to be converted
+ * @param endp	Updated to point to the first character not converted
+ * @return value decoded from string (0 if invalid)
+ *
+ * Converts a decimal string to an unsigned long. If there are invalid
+ * characters at the end these are ignored. In the worst case, if all characters
+ * are invalid, 0 is returned
+ */
+unsigned long dectoul(const char *cp, char **endp);
+
 /**
  * strict_strtoul - convert a string to an unsigned long strictly
  * @param cp	The string to be converted