vsprintf:fix: Change type returned by ustrtoul

The ustrtoul shall convert string defined size (e.g. 1GiB) to unsigned
long type (as its name implies).

Up till now it had returned int, which might cause problems with large
numbers (GiB range), when interpreted as U2 signed numbers.

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index b7a79c0..3c432f8 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -103,7 +103,7 @@
 	return simple_strtoul(cp, endp, base);
 }
 
-int ustrtoul(const char *cp, char **endp, unsigned int base)
+unsigned long ustrtoul(const char *cp, char **endp, unsigned int base)
 {
 	unsigned long result = simple_strtoul(cp, endp, base);
 	switch (**endp) {