crypto: mxs-dcp - Implement sha import/export

The mxs-dcp driver fails to probe if sha1/sha256 are supported:

[    2.455404] mxs-dcp 80028000.dcp: Failed to register sha1 hash!
[    2.464042] mxs-dcp: probe of 80028000.dcp failed with error -22

This happens because since commit 8996eafd ("crypto: ahash - ensure
statesize is non-zero") import/export is mandatory and ahash_prepare_alg
fails on statesize == 0.

A set of dummy import/export functions were implemented in commit
9190b6fd ("crypto: mxs-dcp - Add empty hash export and import") but
statesize is still zero and the driver fails to probe. That change was
apparently part of some unrelated refactoring.

Fix by actually implementing import/export.

Signed-off-by: Dan Douglass <dan.douglass@nxp.com>
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>