crypto: caam - fix memory corruption in ahash_final_ctx

When doing pointer operation for accessing the HW S/G table,
a value representing number of entries (and not number of bytes)
must be used.

Cc: <stable@vger.kernel.org> # 3.6+
Fixes: 045e3678

 ("crypto: caam - ahash hmac support")
Signed-off-by: Horia Geant? <horia.geanta@freescale.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>