lib/string.c: simplify strnstr()

Signed-off-by: André Goddard Rosa <andre.goddard@gmail.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Joe Perches <joe@perches.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/string.c

@@ -689,13 +689,13 @@ EXPORT_SYMBOL(strstr);
  */
 char *strnstr(const char *s1, const char *s2, size_t len)
 {
-	size_t l1 = len, l2;
+	size_t l2;
 
 	l2 = strlen(s2);
 	if (!l2)
 		return (char *)s1;
-	while (l1 >= l2) {
+	while (len >= l2) {
-		l1--;
+		len--;
 		if (!memcmp(s1, s2, l2))
 			return (char *)s1;
 		s1++;