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/BuS/eb_cpu5282/eb_cpu5282.c b/board/BuS/eb_cpu5282/eb_cpu5282.c
index 5829299..b739bc3 100644
--- a/board/BuS/eb_cpu5282/eb_cpu5282.c
+++ b/board/BuS/eb_cpu5282/eb_cpu5282.c
@@ -194,13 +194,13 @@
 	printf("Init Video as ");
 	s = env_get("displaywidth");
 	if (s != NULL)
-		display_width = simple_strtoul(s, NULL, 10);
+		display_width = dectoul(s, NULL);
 	else
 		display_width = 256;
 
 	s = env_get("displayheight");
 	if (s != NULL)
-		display_height = simple_strtoul(s, NULL, 10);
+		display_height = dectoul(s, NULL);
 	else
 		display_height = 256;
 
@@ -234,8 +234,8 @@
 
 	switch (argc) {
 	case 3:
-		side = simple_strtoul(argv[1], NULL, 10);
-		bright = simple_strtoul(argv[2], NULL, 10);
+		side = dectoul(argv[1], NULL);
+		bright = dectoul(argv[2], NULL);
 		if ((side >= 0) && (side <= 3) &&
 			(bright >= 0) && (bright <= 1000)) {
 			vcxk_setbrightness(side, bright);