crypto: testmgr - fix overlap in chunked tests again

Commit 7e4c7f17 ("crypto: testmgr - avoid overlap in chunked tests")
attempted to address a problem in the crypto testmgr code where chunked
test cases are copied to memory in a way that results in overlap.

However, the fix recreated the exact same issue for other chunked tests,
by putting IDX3 within 492 bytes of IDX1, which causes overlap if the
first chunk exceeds 492 bytes, which is the case for at least one of
the xts(aes) test cases.

So increase IDX3 by another 1000 bytes.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>