ieee1275: add nvme support within ofpath

ieee1275: add nvme support within ofpath

Add NVMe support within ofpath.

The Open Firmware text representation for a NVMe device contains the
Namespace ID. An invalid namespace ID is one whose value is zero or whose
value is greater than the value reported by the Number of Namespaces (NN)
field in the Identify Controller data structure.  At the moment  only a
single Namespace is supported, therefore the value is currently hard coded
to one.

Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>