lib: correct link to the original source for div64_u64

The code refers to an invalid url
http://www.hackersdelight.org/HDcode/newCode/divDouble.c.txt

The correct url is
http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

lib/div64.c

@@ -127,7 +127,7 @@ EXPORT_SYMBOL(div64_u64_rem);
  * by the book 'Hacker's Delight'.  The original source and full proof
  * can be found here and is available for use without restriction.
  *
- * 'http://www.hackersdelight.org/HDcode/newCode/divDouble.c.txt'
+ * 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt'
  */
 #ifndef div64_u64
 u64 div64_u64(u64 dividend, u64 divisor)