Add support to the nx-842-pseries.c driver for running in little endian
mode.

The pSeries platform NX 842 driver currently only works as big endian.
This adds cpu_to_be*() and be*_to_cpu() in the appropriate places to
work in LE mode also.
Signed-off-by: NDan Streetman <ddstreet@ieee.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>