powerpc/nvram: Generalize code for OS partitions in NVRAM

Adapt the functions used to create and write to the RTAS-log partition
to work with any OS-type partition.

Signed-off-by: Jim Keniston <jkenisto@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 files changed