crypto: skcipher - Use eseqiv even on UP machines

Previously we would use eseqiv on all async ciphers in all cases,
and sync ciphers if we have more than one CPU.  This meant that
chainiv is only used in the case of sync ciphers on a UP machine.

As chainiv may aid attackers by making the IV predictable, even
though this risk itself is small, the above usage pattern causes
it to further leak information about the host.

This patch addresses these issues by using eseqiv even if we're
on a UP machine.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Acked-by: David S. Miller <davem@davemloft.net>