powerpc: Add static fields to ibm,client-architecture call

This patch adds 2 fields to the ibm_architecture_vec array.

The first of these fields indicates the number of cores which Linux can
boot.  It does not account for SMT, so it may result in cpus assigned to
Linux which cannot be booted.  A second patch follows that dynamically
updates this for SMT.

The second field just indicates that our OS is Linux, and not another
OS.  The system may or may not use this hint to performance tune
settings for Linux.

Signed-off-by: Joel Schopp <jschopp@austin.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>