crypto: omap-sham - fix software fallback handling

If we have processed any data with the hardware accelerator (digcnt > 0),
we must complete the entire hash by using it. This is because the current
hash value can't be imported to the software fallback algorithm. Otherwise
we end up with wrong hash results.

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