crypto: atmel-sha - redefine SHA_FLAGS_SHA* flags to match SHA_MR_ALGO_SHA*

This patch modifies the SHA_FLAGS_SHA* flags: those algo flags are now
organized as values of a single bitfield instead of individual bits.
This allows to reduce the number of bits needed to encode all possible
values. Also the new values match the SHA_MR_ALGO_SHA* values hence
the algorithm bitfield of the SHA_MR register could simply be set with:

mr = (mr & ~SHA_FLAGS_ALGO_MASK) | (ctx->flags & SHA_FLAGS_ALGO_MASK)

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