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/board/compulab/common/eeprom.c b/board/compulab/common/eeprom.c
index 5206cf5..b41c64d 100644
--- a/board/compulab/common/eeprom.c
+++ b/board/compulab/common/eeprom.c
@@ -153,7 +153,7 @@
 	 */
 	if (cl_eeprom_layout == LAYOUT_LEGACY) {
 		sprintf(str, "%x", board_rev);
-		board_rev = simple_strtoul(str, NULL, 10);
+		board_rev = dectoul(str, NULL);
 	}
 
 	return board_rev;