crypto: mxs-dcp - fix type of ret for wait_for_completion_timeout

return type of wait_for_completion_timeout is unsigned long not int, this
patch changes the type of ret from int to unsigned long.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>