crypto: talitos - don't check the number of channels at each interrupt

The number of channels is known from the beginning, no need to
test it everytime.
This patch defines two additional done functions handling only channel 0.
Then the probe registers the correct one based on the number of channels.

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