crypto: nx - fix nx-842 pSeries driver minimum buffer size

Reduce the nx-842 pSeries driver minimum buffer size from 128 to 8.
Also replace the single use of IO_BUFFER_ALIGN macro with the standard
and correct DDE_BUFFER_ALIGN.

The hw sometimes rejects buffers that contain padding past the end of the
8-byte aligned section where it sees the "end" marker.  With the minimum
buffer size set too high, some highly compressed buffers were being padded
and the hw was incorrectly rejecting them; this sets the minimum correctly
so there will be no incorrect padding.

Signed-off-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>