crypto: talitos - talitos_ptr renamed ptr for more lisibility

Linux CodyingStyle recommends to use short variables for local
variables. ptr is just good enough for those 3 lines functions.
It helps keep single lines shorter than 80 characters.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>