crypto: iaa - Do not clobber req->base.data

The req->base.data field is for the user and must not be touched by
the driver, unless you save it first.

The iaa driver doesn't seem to be using the req->base.data value
so just remove the assignment.

Fixes: 09646c98 ("crypto: iaa - Add irq support for the crypto async interface")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>