crypto: nx - simplify pSeries nx842 driver

Simplify the pSeries NX-842 driver: do not expect incoming buffers to be
exactly page-sized; do not break up input buffers to compress smaller
blocks; do not use any internal headers in the compressed data blocks;
remove the software decompression implementation; implement the pSeries
nx842_constraints.

This changes the pSeries NX-842 driver to perform constraints-based
compression so that it only needs to compress one entire input block at a
time.  This removes the need for it to split input data blocks into
multiple compressed data sections in the output buffer, and removes the
need for any extra header info in the compressed data; all that is moved
(in a later patch) into the main crypto 842 driver.  Additionally, the
842 software decompression implementation is no longer needed here, as
the crypto 842 driver will use the generic software 842 decompression
function as a fallback if any hardware 842 driver fails.

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