PPC: KVM: add support for LPCR

The LPCR special purpose register was introduced with the PowerPC 970MP family.

This patch initializes LPCR for the following families:
- 970 MP
- POWER5+
- POWER7
- POWER8

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>