crypto: nx - don't err if compressed output > input

Return success instead of error if compression succeeds but the output is
larger than the input.

It's unlikely that the caller will use the compressed data since it's
larger than the original uncompressed data, but there was no error and
returning an error code is incorrect.  Further, for testing small input
buffers, the output is likely to be larger than the input and success
needs to be returned to verify the test.

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