crypto: kpp, (ec)dh - fix typos

While here, add missing argument description (ndigits).

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/dh_helper.c

@@ -3,9 +3,9 @@
  * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
  *
  * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public Licence
+ * modify it under the terms of the GNU General Public License
  * as published by the Free Software Foundation; either version
- * 2 of the Licence, or (at your option) any later version.
+ * 2 of the License, or (at your option) any later version.
  */
 #include <linux/kernel.h>
 #include <linux/export.h>