ibm: Create p10bmc build target

Replace rainier with p10bmc as build target. Keep the rainier.conf as a
symlink to p10bmc.conf to allow the transition. Remove the rainier.conf
and the machine override from p10bmc.conf in a later commit to complete
the replacement.

Tested: Built rainier and p10bmc and checked for some files/service
        units to exist on both.

Change-Id: Ic8c8c6ffbc3507fbd9c692da259e37ae695359a6
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/meta-ibm/conf/local.conf.sample b/meta-ibm/conf/local.conf.sample
index 4b70cad..9f2228b 100644
--- a/meta-ibm/conf/local.conf.sample
+++ b/meta-ibm/conf/local.conf.sample
@@ -1,6 +1,6 @@
 #MACHINE ?= "mihawk"
+#MACHINE ?= "p10bmc"
 #MACHINE ?= "swift"
-#MACHINE ?= "rainier"
 MACHINE ??= "witherspoon"
 DISTRO ?= "openbmc-witherspoon"
 PACKAGE_CLASSES ?= "package_rpm"