crypto: api - remove CRYPTOA_U32 and related functions

According to the advice of Eric and Herbert, type CRYPTOA_U32
has been unused for over a decade, so remove the code related to
CRYPTOA_U32.

After removing CRYPTOA_U32, the type of the variable attrs can be
changed from union to struct.

Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>