ibm: kernel: Replace rainier with p10bmc

The IBM rainier system is being replaced with the generic p10bmc name.
Since the rainier.conf file will be renamed p10bmc.conf, add the device
tree files for all p10 systems that will be supported with the p10bmc
name (rainier, everest).

Change-Id: I10983b913d8a2ae98ed4d327131b864f2df96a0c
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>