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/cmd/log.c b/cmd/log.c
index 72380c5..c377aee 100644
--- a/cmd/log.c
+++ b/cmd/log.c
@@ -352,7 +352,7 @@
 	if (argc < 7)
 		return CMD_RET_USAGE;
 	cat = log_get_cat_by_name(argv[1]);
-	level = simple_strtoul(argv[2], &end, 10);
+	level = dectoul(argv[2], &end);
 	if (end == argv[2]) {
 		level = log_get_level_by_name(argv[2]);
 
@@ -366,7 +366,7 @@
 		return CMD_RET_USAGE;
 	}
 	file = argv[3];
-	line = simple_strtoul(argv[4], NULL, 10);
+	line = dectoul(argv[4], NULL);
 	func = argv[5];
 	msg = argv[6];
 	if (_log(cat, level, file, line, func, "%s\n", msg))