PowerPC: Add TS bits into msr_mask

During migration, after MSR bits is synced, cpu_post_load() will use
msr_mask to determine which PPC MSR bits will be applied into the target
side. Hardware Transaction Memory(HTM) has been supported since Power8,
but TS0/TS1 bit was not in msr_mask yet. That will prevent target KVM
from loading TM checkpointed values.

This patch adds TS bits into msr_mask for Power8, so that transactional
application can be migrated across qemu.

Signed-off-by: Simon Guo <wei.guo.simon@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>