The input parameter check in acc_get_sgl is redundant. The
caller has been verified once. When the check is performed for
multiple times, the performance deteriorates.

So the redundant parameter verification is deleted, and the
index verification is changed to the module entry function for
verification.
Signed-off-by: Chenghai Huang <huangchenghai2@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>