In doing so, sha512 sized keys would not fit with the current
descriptor inlining mechanism, so we now calculate whether keys
should be referenced instead by pointers in the shared descriptor.

also, use symbols for descriptor text lengths, and, ahem, unmap and
free key i/o memory in cra_exit.
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>