crypto: testmgr - delete some redundant code

Delete sg_data function, because sg_data function definition same as
sg_virt(), so need to delete it and use sg_virt() replace to sg_data().

Signed-off-by: Kai Ye <yekai13@huawei.com>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>