kconfig: util: Fix typo in comment

sting replaced with string
Signed-off-by: Thomas Weber <weber@corscience.de>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

scripts/kconfig/util.c

@@ -72,7 +72,7 @@ int file_write_dep(const char *name)
 }
 
 
-/* Allocate initial growable sting */
+/* Allocate initial growable string */
 struct gstr str_new(void)
 {
 	struct gstr gs;