crypto: nx - rename nx842_{init, exit} to nx842_pseries_{init, exit}

While there is no technical reason that both nx-842.c and
nx-842-pseries.c can have the same name for the init/exit functions, it
is a bit confusing with initcall_debug. Rename the pseries specific
functions appropriately

Signed-off-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>