rainier: software manager mtd names

The rainier filesystem is in a bit of flux right now. Just do the basics
for now.

(From meta-ibm rev: f86820a1b7fb22606ee4de8486b21c3567e36332)

Change-Id: Idfaac713628d1c21d04a129d4231e47b86343339
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>