crypto: talitos - remove to_talitos_ptr_len()

to_talitos_ptr() and to_talitos_ptr_len() are always called together
in order to fully set a ptr, so lets merge them into a single
helper.

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