crypto: omap-sham - add proper load balancing support for multicore

The current implementation of the multiple accelerator core support for
OMAP SHA does not work properly. It always picks up the first probed
accelerator core if this is available, and rest of the book keeping also
gets confused if there are two cores available. Add proper load
balancing support for SHA, and also fix any bugs related to the
multicore support while doing it.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>