crypto: atmel-sha - fix algorihtm registration

This patch implements the missing .import() and .export() mandatory
hooks for asynchronous hash algorithms. It also sets the relevant, non
zero, value for the .statesize field when declaring the supported SHA
algorithms. Indeed a zero value of .statesize prevents the algorithm from
being registered.

Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>