As it stands we use chainiv for sync algorithms and eseqiv for
async algorithms.  However, when there is more than one CPU
chainiv forces all processing to be serialised which is usually
not what you want.  Also, the added overhead of eseqiv isn't that
great.

Therefore this patch changes the default sync geniv on SMP machines
to eseqiv.  For the odd situation where the overhead is unacceptable
then chainiv is still available as an option.

Note that on UP machines chainiv is still preferred over eseqiv
for sync algorithms.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>